The Sapperton Canal Tunnel is a tunnel on the Thames and Severn Canal near Cirencester in Gloucestershire, England. With a length of , it was the longest tunnel of any kind in England from 1789 to 1811. Construction, following an Act of Parliament, began in 1784. Twenty-six shafts were dug along the line of the tunnel and workfaces dug in each direction eventually joining up before the diameter of the tunnel was expanded. Difficulties were encountered related to strata of Great Oolite (solid limestone) and Fuller's Earth clay. These caused roof falls and narrowing of the channel which continued after the tunnel opened in 1789 and required frequent maintenance. The stone portals at either end are listed buildings. Boats passed through by legging until 1911. The canal was abandoned by 1933 and subsequent roof falls mean that it is no longer navigable. Cotswold Canals Trust have proposed restoration. History The Thames and Severn Canal was authorised by an Act of Parliament on 17 April 1783 but details of the tunnel had not been worked out, and arguments about its size continued for two to three months. Regular barges on the Severn were trows which were wide; those on the Thames were Thames barges, wide. The only long tunnel in the country at the time was Harecastle Tunnel, 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 below ground at its deepest point. It was expected to take four years to complete, beginning in early 1784. To speed the work, 26 shafts were sunk for many simultaneous workfaces, the deepest of which was . Small tunnels, known as headings, were dug in two different directions from the base of each shaft and the spoil lifted up the shaft and dumped in Spoil tips above the route of the canal. A small temporary railway was later installed to take workers into the tunnel and remove waste materials. The use of explosives to expand the headings to the full size of the tunnel meant that