There is a stretch of the M1 motorway between Sprucefield and Moira where the asphalt sits on top of an 18th-century canal bed. When the road was built in 1965, the engineers simply filled in the canal and laid the tarmac over it - 7.7 miles of summit level, ten masonry locks, towpaths, lock-keeper's cottages, all gone under the concrete. The Lagan Canal had only been closed seven years. Nobody at the time imagined that within a generation people would want it back. Today's restoration campaigners face a slightly absurd task: most of the central section no longer exists, and a six-lane motorway sits on the route. They are working on the bits that survived. There turn out to be quite a lot of them.
The River Lagan at Moira sits only 10 kilometres from Lough Neagh, the largest freshwater lake in Britain or Ireland, and the terrain between them is flat. The first proposal to dig a connecting canal was made in 1637 but nothing happened. By the 1750s, with coal newly discovered in east Tyrone on the far shore of Lough Neagh and the Newry Canal already proving the concept, Parliament took the question up again. An Act of 1753 authorised the work - but the Irish state was broke. The canal was instead funded by a special tax on alcohol in the districts the canal would pass through: one penny per gallon on ale, fourpence on spirits, levied for eleven years. Construction began in 1756 under the engineer Thomas Omer, and the first 14-mile river-navigation section to Lisburn was opened in September 1763 when a 60-ton lighter called the Lord Hertford brought 45 tons of coal and timber up from Belfast.
The river-navigation worked badly. Floods washed away the banks in winter, the local linen-bleaching industry needed the same water the canal wanted, and beyond Sprucefield the work simply stopped. A young engineer named Robert Whitworth - James Brindley's chief surveyor - assessed the project in 1768 and recommended replacing the river section with a proper canal. Nobody had the money. In 1779 a private company was formed, dominated by the immensely wealthy Marquess of Donegall, with most of the rest of the shareholders being landed gentry or peers. Richard Owen, a veteran of the Leeds and Liverpool Canal, took over construction in 1782. The four Union Locks raised boats from the river to an 11-mile summit level. An aqueduct at Spencer's Bridge took three years to build. The final 10 locks down to Aghalee dropped boats to the lough's level. The Marquess personally bankrolled most of the £62,000 cost - well over £8 million today - and opened the canal on 1 January 1794 by sailing the length of it himself.
For most of the 19th century the Lagan Canal was one of only two commercially successful inland waterways in the north of Ireland. It survived the arrival of the Ulster Railway in the 1840s, paid its first dividend in 1859, and by the 1870s was carrying more than double the traffic it had handled in the 1830s - mostly coal moving up from Belfast and sand and gravel coming down from the Lough Neagh shore for the city's building boom. In the 1920s the canal still moved over 300,000 tons of coal a year between Belfast and Lisburn. Then came lorries. Between 1931 and 1941, downstream traffic on the upper canal collapsed from 29,000 tons to 600 tons. After 1947 there was no traffic at all above Lisburn. The Lagan Navigation Company ran on government subsidies through the late 1940s, kept alive by a legal technicality, until the Inland Navigation Act of 1954 formally closed the upper section. The lower section followed four years later. The last boat went through in July 1958.
Some things in Britain's industrial heritage are lost slowly. The Lagan Canal was lost fast. In 1965 the Northern Ireland government decided that the obvious route for the new M1 motorway from Belfast to Dungannon was along the old canal's central level, where the line had already been surveyed and the land secured. The engineers excavated the lock chambers, removed the masonry where convenient, filled in the cut, and ran the carriageways over the top. There was little public objection. Canals were considered antique transportation; motorways were the future. The 7.7-mile stretch between Moira and Sprucefield is now under the M1's middle lanes. If you drive it today you can still spot the old route in flashes: a fragment of stone bridge in a farmer's field, a straight line of mature trees marking a towpath, a brick warehouse facing nothing where its loading wharf used to be.
Where the canal escaped the motorway, things are happening. The Lagan Navigation Trust, founded in 2008 and renamed in 2016, has identified the remaining sections as a single restorable corridor. Lock 12 at Lisburn has been restored to navigable condition. Lock 3 at Newforge, with its lock-keeper's cottage, has been rebuilt with Heritage Lottery funding. A 1.5-kilometre stretch of towpath at Aghagallon - the first restored section of the privately-owned final ten locks - has been reopened to the public. A £4 million project to build a new lock at Stranmillis Gateway in south Belfast, replacing the inefficient pen weir that currently dams the river there, is funded and underway. The old lock-keepers' cottages have become heritage buildings. All the locks are now scheduled monuments. The feasibility study concluded that the canal could be a major recreational waterway, with one caveat: that thing about the motorway. They are working on it.
The Lagan Canal traces a 27-mile arc from Belfast city centre at 54.60°N, 5.92°W south-west to the shores of Lough Neagh near Aghalee at 54.54°N, 6.27°W. From the air, look for the broad River Lagan emerging from central Belfast and threading south-west through the Lagan Valley - the canal once paralleled the river. The M1 motorway, which buried the central section in 1965, is the dominant west-south-west axis between Lisburn and Moira. Lough Neagh itself, the largest freshwater lake in Britain or Ireland at 153 square miles, dominates the air picture to the west - it lies at the geographic centre of Northern Ireland and is unmissable from cruising altitude. Belfast City Airport (EGAC) is 3 nautical miles east of the canal's start; Belfast International (EGAA) is on the lough's eastern shore. Recommended viewing altitude: 3,000-7,000 feet to take in the entire former route from city to lake.