Although the Thames and Severn Canal was authorised by an Act of Parliament on 17 April 1783, the details of the tunnel had not been worked out, and arguments about its size continued for two or three months. Boats on the Severn were trows which were wide, while those on the Thames were Thames barges, which were wide. The only long tunnel in the country at the time was Harecastle Tunnel, which was suitable for narrow boats just wide. A party of Commissioners from the Thames thought that the cost of a wide tunnel would be prohibitive, and that it should be built for narrow-beam boats, with the trows or barges unloading their cargos at each end of the tunnel. By late summer, the decision had been taken to build a broad tunnel, high and wide, and the company advertised for tunnellers in September. The tunnel would be long, and was expected to take four years to complete, beginning in early 1784. In order to speed the work, 25 shafts were sunk along its length, to provide multiple workfaces, the deepest of which was. The construction contract was awarded to Charles Jones, who managed to build about one third of it, but then had financial difficulties, and so a number of other contractors were engaged to work on smaller sections. The tunnel was opened on 20 April 1789, after five years of construction. It has no towpath; boats were propelled through the tunnel by legging. There were some defects in the workmanship, as it had to be closed for ten weeks after only a year, while repairs were carried out. It was superseded as the longest canal tunnel in England in 1811 by the Huddersfield Narrow Canal's Standedge Tunnel, which was long when built, later extended to to accommodate the adjacent railway tunnel, and remains the highest, longest and deepest canal tunnel in Britain - though, unlike Sapperton, Standedge can only accommodate. Strood Tunnel on the Thames and Medway Canal was also longer at when it opened in 1824, but was cut in two in 1830 by opening out a short section to create a passing basin. Sapperton Tunnel was passable until at least 1966 but is now blocked by roof collapses over several hundred yards, mainly in sections where the ground is fuller's earth. Restoration is proposed by the Cotswold Canals Trust as part of their project to re-open the canal route from Thames to Severn. The trust operates tourist boat trips into the tunnel in winter months. The Sapperton railway tunnel, on the Golden Valley Line, follows a broadly similar route under the 'Cotswold Edge'. There have been proposals for a national network of canals and aqueducts to bring water from the River Severn toward the Thames Basin and London; if such a plan is realised the Sapperton Canal Tunnel could be utilised to transport water.
In fiction
In Hornblower and the Atropos by C.S. Forester, Hornblower helps the boatman "leg" through Sapperton Tunnel after the boatman's assistant is incapacitated. Forester spends the first two chapters of the book on the canal-boat journey, Roughly a third of the first chapter is devoted to the tunnel. In the novelGone by Mo Hayder the tunnel is used extensively as a location in this crime thriller. An episode of Midsomer Murders titled The Green Man was partly filmed at the tunnel.
