INTRODUCTION
Since early times we humans have sought to understand and document the lands in which we live and travel. Whether this has been through simple etchings on rocks, cave paintings, markers such as milestones and signposts or the drawing of complex maps, navigational aids have long formed a vital part of humankind's relationship to the land.
In the 20th century, Britain's national mapping agency, Ordnance Survey, created a system of numbered gridlines, 1km apart, criss-crossing the entire country from north to south and from east to west. Despite more recent innovations in the digital age, these gridlines are still in popular use for precisely specifying locations anywhere from the Scily Isles in the south west to the tip of Shetland in the north east.
Crossing the Lines is a project to make photographs at locations close to my home in West Kirby where the OS gridlines intersect. It is an ongoing project and this web page is a work in progress.
In undertaking this project, I have set myself two requirements:
(i) each intersection must be visible within the frame of the photograph
(ii) locations must be reached on foot, by bike or by public transport.
In a few cases it has not been possible to see the position of an intersection e.g. because it lies behind a high wall. In these cases I have gone as close as I can and then made an image that would show the intersection if the obstruction were not there.
In the course of this project I have gone to places virtually on my doorstep that I didn't know existed. I have learned about places of which I previously knew nothing and I have taken photographs of places that I would never have thought justified getting my camera out of its bag. It has been tremendously rewarding and I plan to slowly extend my reach further eastwards across the Wirral.
THE IMAGES
Scrolling down the page, the locations are ordered in ascending order of grid reference. As the Ordnance Survey lines are numbered from west to east and then from south to north, this means my images start in the west and work their way eastwards. Along each vertical gridline, they start in the south and progress northwards. On the Wirral, all map references begin with the letters SJ.
Below each image is some text about the location and also a thumbnail image indicating the position of the gridline intersection within the frame. These thumbnails can be enlarged by clicking.
SJ 190 870 - Between the islands
Off shore from West Kirby lie three tidal islands; Hilbre Island, Middle Eye and Little Eye (which get their names from the Norwegian word for island; øy). The islands can be reached on foot at low tide. Between Little Eye and Middle Eye lies a long chain of sandstone rocks that barely protrude above the sand. When the tide is partly in or out the sea swirls around them in an attractive but fleeting transition state of wet and dry, solid and liquid. Many of the rocks are covered by a dark seaweed which, whilst being no expert, I believe to be called Knotted Wrack. If you know otherwise, please let me know via my contact page - thank you.
SJ 190 880 - East of Hilbre Island
Looking from Hilbre Island back towards Hoylake on the mainland lie some of the dangerous quicksands that are exposed at low tide around the Wirral coast. With the Mersey having the second-highest tidal ranges in the UK15, it is easy to be caught out by the incoming tide. Most locals know the importance of checking the tides and following the safe route when walking out to the islands but, even so, it is not uncommon for the RNLI rescue hovercraft to be called out to help people who find themselves stuck fast in the sand with the tide rapidly advancing.
SJ 200 860 - Tanskey Rocks
To the south of Little Eye lie another group of low-lying rocks; Tanskey Rocks (from the Norse "Tonnsker") which can be found out to sea beyond West Kirby Marine Lake. The name West Kirby, along with many other Wirral places, derives its name from Norse which arrived on the peninsula along with the Vikings in 9202AD. Nowadays the rocks only protrude a few centimetres above the level of the surrounding sand but, given the relentless silting up of the Dee Estuary, it is likely that they were once significant geological features. Sources: Cheshire Now, Margaret E. Marker MA, M.AG.SC.
SJ 200 870 - near Little Eye
Another image taken out on the sands that surround the north west corner of the Wirral, this time while the tide is in. SJ 200 870 lies slightly north east of Little Eye and this image looks north west towards Hilbre Island and Middle Eye with the intersection in the immediate foreground. Although from this viewpoint it looks as if the two islands are joined, there is, in fact, some 250m between them. Despite appearances, I was only standing in about 15cm of water to take this photograph.
SJ 200 880 - West of Hoylake
The sands to the east of Hoylake are reputed to be dangerous because of quicksands and the fast tides. Visitors to Hilbre Island are told not to cross the sands at this point. This image, taken not far from the shore and precisely at SJ 200 880, depicts the stretch of tidal sand and silt between Hilbre Island and the mainland - a distance of just over 1km. It is the same part of the estuary as depicted in the image of SJ 190 880 but this time we are looking west into the setting sun.
The ripples which cover the sands stretch for kilometres, not only making walking more tiring than usual, but also retaining water to soak the feet of anyone venturing out in trainers rather than waterproof footwear.
SJ 200 890 - Beyond Red Rocks
SJ 200 890 is located offshore slightly to the north or Red Rocks in Hoylake. Red Rocks is a group of red sandstone rocks (hence the name) that are usually partly or wholly covered at high tide and this image was taken as the tide was coming in, beginning to cover the rocks. Red sandstone is ubiquitous in the north of the Wirral Peninsula, its colour resulting from a high iron content in the rock.
In the distance in this image can be seen the wind turbines of the Burbo Bank offshore wind farm. The extension of the wind farm, which was completed in 2017, has 32 8MW turbines which (at the time of writing in 2023) are the largest turbines ever used for an offshore wind farm, with a rotor diameter of 164 meters and a height of 195 meters. They are also among the most powerful turbines in the world, as they can produce more electricity than any other turbine of the same size.
SJ 210 860 - West Kirby Marine Lake
This intersection is located close to the south-western corner of West Kirby Marine Lake. In this image it is to the right of the "lamp stand" marker post (a navigation aid properly known as a "perch"). The Marine Lake was originally built by the Victorians in 1899 for swimming and recreational boating and was later extended in 1985 to its current size of 21 hectares (52 acres), making it the largest marine lake in the UK.
SJ 210 870 - Lingdale Court
Lingdale Court (the building in the left) is small complex of apartments overlooking West Kirby beach. This image was taken from the beach shortly after the high tide, showing the growth of vegetation that has colonised parts of the beach in recent years. The pools and dunes between here and Hoylake provide an ideal habitat for natterjack toads which are one of the UK's rarest - and loudest - species of amphibian.
SJ 210 880 - Royal Liverpool Golf Club
The Royal Liverpool Golf Club, founded in 1869, lies on the eastern shores of the Dee Estuary between West Kirby and Hoylake. The western side of the course features sand dunes that typify this stretch of coast. Since its formation, the club has hosted The Open Championship - the oldest golf championship in the world - thirteen times and, as such, is one of the most used courses for the championship. Despite its name, "The Open" is only open to male competitors and the Women's Open (founded in 1976) only came to the Royal Liverpool for the first time in 2012.
SJ 210 890 - Hoylake western shore
The north shore of the Wirral is currently undergoing significant habitat change as a result of coastal accretion i.e. the depositing of sand and silt from the Irish Sea and the River Dee. As sea levels rise and deposits accumulate, what was once extensive sandy beaches is now being colonised by new plant and animal life. It has been a highly contentious issue among local residents with two opposing camps which may be crudely characterised as "Save our Beach" and "Let nature take its course". This image shows some of the new vegetation at low tide. The sea has ebbed away leaving puddles, many of which often remain throughout the low tide.
SJ 220 850 - Caldy Beach
Caldy Beach lies on the west coast of the Wirral facing out across the estuary of the River Dee towards North Wales which can be seen in the distance. In the foreground is a rusted metal tank that has been around long enough to become encrusted with barnacles. On the rocks are growths of knotted wrack seaweed (aka Norwegian kelp) which is actually a variety of algae. Knotted wrack features bladders filled with air and it is possible to tell its age by counting these as one bladder forms on each stem each year. In the middle of the image an oystercatcher is just coming into land. They are very common around the shores of the Wirral.
SJ 220 860 - Caldy Road
Caldy Road runs from West Kirby to Caldy which, until the 20th century when it became an upmarket residential area, was largely a farming village. Nowadays Caldy is home to many large detached properties. At the time of writing (August 2025), house prices in Caldy had averaged £920,000 over the last year; nearly four times the £250,000 average for the rest of Wirral. This image was taken with a Lensbaby lens to deliberately add blur to the image and create a sense of mystery. Sources: Rightmove (Caldy), Rightmove (Wirral).
SJ 220 870 - Grange Hill
At 53m above sea level, Grange Hill is one of the high points on the Wirral Peninsula and, being topped with a 15m war memorial, it is visible from miles around. The war memorial, erected in 1922 stands surrounded by a small area of heathland in which this location is found. It is populated mainly by grass, heather, gorse and outcrops of the underlying sandstone and this image depicts an area of gorse that was burned in a recent fire. The extensive views from the hill include the Dee estuary and Hilbre islands, Anglesea (Ynys Môn), the Clwydian Hills, Liverpool Bay and the Sefton coast as well as other parts of north Wirral.
SJ 220 880 - north of Greenbank Road
The area of North Wirral bounded by Grange Hill to the west, Bidston Hill to the east and the Irish Sea to the north is characterised by low-lying marshy land known as the carrs. Drainage of these marshes is afforded by an extensive network drainage ditches, the earliest of which are thought to date back to Roman times. One such ditch terminates at a pumping station on Greenbank Road from where water is pumped out to the Dee Estuary. Intersection SJ 220 880 lies alongside this ditch where, for some reason, the ditch is separated from the adjacent field by a high barbed-wire fence.
SJ 220 890 - Scottish Power
Scottish Power has a training centre in Hoylake where engineers are trained in such matters as electrical safety and wind turbine maintenance. Despite its name, Scottish Power is no longer a Scottish company. It was formed in 1990 through the merger of two publicly-owned electricity boards; North of Scotland Hydro-Electric Board and South of Scotland Electricity Board, privatised a year later and subsequently acquired by Spanish utility company Iberdrola. In 2020 The Observer gave Scottish Power its Worst Customer Service award and in 2021 Which? magazine ranked it as the worst performing supplier for customer service.
SJ 220 900 - Hoylake eastern shore
SJ 220 900 lies on the beach in the middle distance in this image, about 100m beyond the railings. The scene there is similar to that at SJ 210 890. In the foreground of this image is Hoylake Model Boating Lake which recently re-opened after significant repairs and refurbishment. It had lain empty and unusable for several years.
SJ 230 840 - Dee Sailing Club
Dee Sailing Club (DSC) is one of two sailing clubs on the west coast of the Wirral, the other being West Kirby Sailing Club. Founded in 1909, DSC was originally named Heswall Sailing Club but changed its name three years later. Its first club house was in Lower Heswall close to the site of the now closed Sheldrakes restaurant. The estuary has silted up significantly since 1909 and in 1982 the club moved downstream towards the Irish Sea to its present day site at Thurstaston.
SJ 230 850 - Croft Drive East
This intersection lies within the private grounds of a residential property in Caldy, behind the high hedges to the left of the parked car. Caldy features many detached houses in sizeable grounds and was described by the Liverpool Echo as "a millionaire's playground". According to the Echo it is home to local celebrities and footballers including Liverpool and England player Robbie Fowler and former Everton and Liverpool manager Rafa Benitez.
SJ 230 860 - Kings Drive North
Kings Drive North is a short road leading south from Column Road towards Caldy Hill. The road only goes for about 100m before turning into a bridleway which leads through the National Trust's Stapledon Woods to Caldy. Caldy Hill at 79m is another of the highest hills on the Wirral. Alongside Kings Drive North are a few residential properties, one of which is situated at this intersection.
SJ 230 870 - St Michael of all Angels church
I was delighted when I found that this church lies at one of the gridline intersections as I had already photographed it previously as part of my work on modern architecture - see here. It's a great building to photograph as not only is it very eye-catching but it can also be successfully portrayed from several different angles. The actual intersection is in a private back garden behind the church so can't be seen directly from any direction.
SJ 230 880 - Long Rake Farm
SJ 230 880 definitely wins the prize for least interesting intersection so far, lying as it does in the middle of unremarkable farm land to the north of Newton. The actual intersection is close to the gap in this hedge. The photograph was taken with an infrared camera.
SJ 230 890 - The Birket
SJ 230 890 is another intersection located on farm land, close to the far field boundary and before the line of trees in the distance. Along the left hand side of the field runs the River Birket. Barely a trickle at this point close to its source, the Birket begins as a drainage ditch serving the surrounding fields before running from west to east across much of the northern reaches of the Wirral. Along the way it is joined by the "River" Fender and the more appropriately named Arrowe Brook and eventually discharges into the West Float in Birkenhead docks. The sign in the image reminds us of the ridiculously restrictive land access rights that we have in England compared to Scotland's "right to roam" where the general public has access to the vast majority of land, regardless of its ownership.
SJ 230 900 - The Railway pub
Apart from sitting exactly at this intersection, The Railway has another important claim to fame. During its construction in 1938, workmen discovered the remains of a clinker-built boat - in the style of Viking ship building. This would be consistent with the Wirral having been host to significant Viking populations from 902AD onwards. Being on a tight schedule, the workmen were told to cover over the boat and keep building but one of them made a sketch of the boat and its location. This sketch survives to today. Source: Wirral Archaeology CIC.
SJ 230 910 - Meals Beach
Along the north coast of the Wirral, from Hoylake to New Brighton are long flat beaches which form extensive sand and mud flats at low tide. These habitats are important for seabirds and other wildlife and almost all the coast is covered by overlapping statutory designations including Sites of Special Scientific Interest (SSSIs), Special Protection Areas (SPAs) and Special Areas of Conservation (SACs). As the tide ebbs and water recedes from this massive area, fast-flowing channels form that carve their way in attractive and ever-changing patterns out to the Irish Sea. Sources: Gov.UK, Wirral Council.
SJ 240 830 - Thurstaston Beach / England Coastal Path
On the left of this image is Thurstaston Beach and on the right can be seen a stretch of the new England Coastal Path. The path became possible following the Marine and Coastal Access Act 2009 and is being created by Natural England, a public body under the aegis of the Dept. of the Environment. The first length of the path in Dorset opened in 2012 and the section around the Wirral opened in January 2025. Once complete, the whole path with cover the whole of the English coast and will stretch some 2,700 miles. Sources: Gov.UK, Wikipedia.
This location lies in the middle of a field off Station Road which runs in a straight line from Thurstaston to the coast. The road has its unlikely name because there was once a station at its western end; Thurstaston Station on the Birkenhead Railway. This service was built during the mid 1800s to link Birkenhead to Chester and to the manufacturing towns of Lancashire. It had to skirt around the Mersey estuary as the rail tunnel connecting the Wirral to Liverpool didn't open until 1886. A few years after completion of the main line, a branch was built connecting Hooton to West Kirby via Hadlow Road, Neston and the coastal villages along the Dee. This branch was closed in 1962 thanks to the recommendations of Dr. Richard Beeching but the trackbed still exists and has been used to create the Wirral Way, a 20km walking and cycling route from Hooton to West Kirby. Sources: Wikipedia (Birkenhead Railway), Wikipedia (Beeching Cuts), Visit Cheshire.
SJ 240 850 - field, Telegraph Road
What can I say? It's a field behind some houses on Telegraph Road that runs from West Kirby to Heswall! But for lovers of trivia, Telegraph Road is a stretch of the A540 which runs from Chester to Hoylake. It is the only road in the series A540 to A549 that lies entirely within England. All the others are either partly or entirely in Wales. Source: Wikipedia.
SJ 240 860 - Torpenhow
Secluded by trees but lying close to Montgomery Hill, Torpenhow is now a collection of privately-owned residential buildings in extensive grounds. Sharing its name with a village in Cumbria, Torpenhow was originally built in the late 1900s and in the early 20th century became an "open air school" run by the Liverpool Chest Hospital. Such schools were created in the belief that children from inner cities who suffered from respiratory and other diseases would benefit from spending time in the fresh air of the countryside. Sources: Former Children's Homes website, British Newspaper Archive.
SJ 240 870 - Larton Livery
Larton Livery is a stables and horse-riding centre which has diversified into various other businesses including pet-food sales, caravan and motorhome storage, kennels and cattery, a café and fishing ponds. It started life in 1975 when the site was bought by a William Titley to build a private home. Source: Larton Livery website.
SJ 240 910 - Slipway, Wallasey Embankment
Wallasey Embankment (which stretches from Meols to the outskirts of New Brighton) was originally built during the 19th century to prevent flooding of the low-lying carrs to the south. The current concrete embankment was built in the 1970s and 1980s. The intersection can be seen on the embankment a couple of hundred metres in front of the boat. Source: The Flood Hub.
SJ 250 840 - field adjacent to Telegraph Road
This otherwise uninteresting field lies immediately alongside the A540 (Telegraph Road) between Caldy and Heswall. I was lucky enough to photograph it very shortly after the wheat crop had been harvested, leaving this (very small) host of scarlet poppies dancing in the breeze.
SJ 250 850 - paddocks off Sandy Lane, Irby
Alongside Sandy Lane in Irby are a series of fields used mainly as paddocks for horses. Behind the paddocks lies Thurstaston Common which is the largest remaining area of open heathland in Merseyside with a very rich variety of habitats and flora, leading it to being designated as a Site of Scientific Special Interest (SSSI). The common, which is jointly owned by Wirral Council and the National Trust, is an important habitat for sparrowhawks, tawny owls, great and lesser spotted woodpeckers and others which are all known to breed there. Source: Natural England Designated Sites.
SJ 250 860 - field, Hill Bark Road
SJ 250 860 lies in a field just to the south of Hill Bark Road and it can be seen from the "permissive bridleway" which runs from north to south alongside Greasby Brook. Peering through a gap in the hedge that lines the path we can see Roodee Cottages, a pair of 19th century private houses. Greasby Brook is small stream which runs for some 5km before joining the Arrowe Brook near Saughall Massey. According to pollution monitoring group Top Of The Poops, water company United Utilities dumped sewage into Greasby Brook 36 times in 2024. Sources: Wirral Globe, Top of the Poops.
SJ 250 870 - Langstone Avenue, Greasby
I'm sure the lucky occupants of this house will be thrilled to bits if they ever discover that the intersection SJ 250 870 sits firmly on their front drive! Langstone Avenue is on a housing estate on the west side of Greasby, thought to have been built in the late 1990s.
SJ 270 940 - Wreck of the SS Denham
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SJ 280 930 - Mockbeggar Wharf
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SJ 290 930 - Wallasey Grove Road station
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SJ 300 910 - Bidston Dock
Bidston Dock, originally known as the West Float Extension, was excavated from the former Bidston Moss peat bog. The dock opened in 1933 and during its working life, was used, among other things, for the transport of iron ore which was bound for the steelworks at Shotton. It was later closed in 2003 and used as a landfill site though the old dockside railway tracks and bollards can still be seen in places. The site is now owned by Peel Holdings and fenced off pending future development as part of the Wirral Waters regeneration project. As of August 2025, Peel had submitted a planning application for a major health and fitness club to be run by David Lloyd Leisure. Sources: Etymonline, Liverpool Museums, Wikipedia, Peel Holdings.
SJ 300 900 - Avon Street, Birkenhead
Avon Street is a residential street of mainly early 20th century houses. It lies to the south of West Float in the Birkenhead Docks and close to Birkenhead North Merseyrail station.
SJ 320 890 - Birkenhead Park
Birkenhead Park, opened in 1847, is often regarded as the world’s first publicly funded park. Designed by landscape architect Joseph Paxton (who also designed the Crystal Palace in London), it was created to provide green space for for the residents of Birkenhead at a time of rapid industrial expansion. Its innovative design, blending open meadows, woodlands, and ornamental lakes, influenced the development of urban parks worldwide, including New York’s Central Park. Despite later becoming an English Heritage Grade I listed landscape, by the end of the 20th century the park had become neglected and run down. During the early years of the 21st century it underwent an £11 million major restoration project jointly funded by Wirral Council, the Heritage Lottery Fund and the European Union. Source: Wikipedia.
SJ 320 890 - Vue Cinema, Birkenhead
The Vue is a seven-screen cinema that opened in 1999, originally as Warner Village Cinema and which rebranded as Vue after changing hands in 2004 . At the time of this photograph, the Vue was surrounded by road works and traffic reconfiguration works as part of Wirral Council's multi-million pound regeneration scheme that was running well beyond its planned completion date and well over budget. The works have made getting around Birkenhead difficult, whether on foot, bike or other transport and have become hugely controversial within the council. Sources: Historic England, The Post.
SJ 320 900 - East Float dock
The East Float is part of the Birkenhead Docks complex which form the boundary between Wallasey and Birkenhead. Unlike the Liverpool Docks, which were largely built out from the shore of the Mersey, the Birkenhead Docks were created inland by enclosing the natural tidal inlet known as Wallasey Pool. Built between 1851 and 1860, the largest of the docks is the Great Float which extends some 3km inland from the Mersey. The two floats are separated by a narrow straight which is spanned by the Duke Street bascule bridge. In the foreground is seen the wreck of the Sarsia, a former research vessel which sank in 1998. Sources: Wikipedia, Geograph.
SJ 330 870 - A41 Pallet Services
A41 Pallet Services is a small local business supplying pallets to local trades. According to trade body TIMCON (Timber Packaging and Pallet Confederation), there are estimated to be around 250 million wooden pallets in circulation in the UK, with some 40 million new ones being manufactured each year. Source: Warehouse & Logistics News.
SJ 330 890 - Land Registry office, Woodside
The Land Registry is a government agency with responsibility for recording the ownership of all land in England and Wales. This is one of the 14 regional offices from which the Registry operates. Despite being established in 1862, the agency still has records covering only around 87% of land (by area) with the remainder being unregistered. This is possible because it is currently only necessary to register land when it is bought or sold but not when it is inherited. As a result, large swathes of land which have remained in the hands of aristocratic families, the church or the crown, have never had to be registered. Sources: Wikipedia, Who Owns England.
SJ 340 870 - Rock Ferry Pier
Earliest records indicate the presence of a ferry service from Rock Ferry to Liverpool as far back as the 1300s, with a steam service being introduced in the early 1700s, making use of the landing stage on the pier. The ferry was discontinued in 1939, mainly because of declining demand following the opening of the Mersey Railway, linking the Wirral to Liverpool in 1886. The end of the ferry service led, in the 1950s, to the removal of the landing stage and the demolition of the terminal building. The pier subsequently became part of the Tranmere Oil Terminal which is sited immediately adjacent. On the left of this photo can be seen the oil tanker Seychelles Patriot which, at the time of this photograph in August 2025, had recently arrived from Rotterdam. The oil terminal, which opened in 1960, is linked by a 24km pipeline to Eastham and Stanlow oil refineries and supplies all the crude oil used by them. Sources: Wikipedia (Rock Ferry), Wikipedia (Mersey Railway), Wikipedia (Tranmere Oil Terminal), MyShipTracking.com.
SJ 360 800 - Eastham Village
Eastham is one of the oldest villages on the Wirral peninsula, having been inhabited since Anglo Saxon times, with the original village having clustered around the St. Mary's Church. In the churchyard there is an ancient yew tree believed to have been growing since 1152. From the Middle Ages up until the early 20th century there was a ferry service from Eastham to Liverpool, leaving from the jetty close to the Eastham Ferry pub, some 1.5km to the north east of the village. Initially these were sail boats but they were replaced with paddle steamers in the early 1800s but, like the Rock Ferry service, demand declined after the opening of the Mersey Railway in 1886 and eventually led to the end of the ferry service. Sources: Wikipedia (St.Mary's Church), Wikipedia (Eastham).
SJ 370 810 - Eastham Locks
Eastham Locks form the western entrance to the Manchester Ship Canal enabling craft to enter the canal at different states of the tide in the Mersey Estuary. There is only one publicly accessible viewpoint on the Wirral from which the locks can be seen and, even then, it's a very limited view. The canal, which stretches 58km (36 miles) inland to Manchester opened in 1894 and was, at that time, the largest river navigation canal in the world. Its construction was highly contentious because it challenged Liverpool's position as the only major port serving north west England. As it turned out, Manchester grew to be Britain's third busiest port but as ships grew larger they could no longer be accommodated and the Port of Manchester closed in the early 1980s. Like much of the industrial Merseyside, the canal is now owned by Peel Holdings which also owns much of the Liverpool and Birkenhead docks.
SJ 370 800 - Eastham Refinery
Eastham Refinery is one of only seven remaining refineries in the UK that process crude oil. Stanlow Refinery, just a few miles from Eastham is one of the other six. Opened in 1966 as a joint venture between Tarmac Ltd and Phillips Petroleum of America, the refinery originally made materials including bitumen and marine diesel. The raw material (crude oil) is delivered by pipeline from Tranmere Oil Terminal (see SJ 340 870). Nowadays the major shareholder in the refinery is Shell. Photographing the refinery isn't easy as it is surrounded by a high metal fence with only small gaps. Attached to the fence are signs stating that duty has not yet been paid on the oil being processed and so stealing it will result in "severe customs penalties" and forfeiture of any vehicle used in the theft. Sources: Concawe, Wikipedia, Companies House.
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About the grid lines
A grid system for use in specifying geographical location in Great Britain was developed in the early 20th century by the Ordnance Survey (OS). Ordnance Survey, the national mapping agency, has it roots in the Jacobite Rebellion of 1745 following which King George II commissioned the compilation of a map of the Highlands in order to assist the British army in subjugation of the clans. As mapping developed in Britain, whilst still heavily relied upon for military purposes, its applications broadened to also encompass civil and fiscal functions such as taxation and planning. In 1935 a review by the Davidson Committee determined that a grid system should be introduced to enable the precise specification of locations. With an eye to a metric future, it was agreed that the grid should be based on 1km squares. The Davidson Review also led to the erection of triangulation pillars (commonly known as “trig points”) on prominent hills and mountains to assist in further mapping of the land.