The clay bricks used in the tunnel were fired at a nearby brickworks; this works used material which had been excavated as spoil from the boring process.

[5][6] During the Second World War, the tunnel was a secondary target for the Luftwaffe bombers that regularly conducted bombing raids against Filton Aerodrome at neighbouring Bristol.

Accordingly, the tunnel has been a long-standing high-priority asset for attention amongst railway maintenance staff, despite the installation of pumps and other measures to remove the water.

[1] During the 2010s, various plans were produced to improve the flooding situation, including the installation of 6.5 kilometres (4.0 mi) of pipes for a new gravity drainage system.

[9] Its installation necessitated the partial removal of an older brick culvert which carries water from the tunnel to the nearby Kingrove river.

[1] As part of the modernisation of the Great Western main line, the route through the tunnel was temporarily closed to traffic between 8 May 2017 and 19 July 2017, and again between 19 August and 15 September 2017.

[10][1] During these closures, the tunnel was retrofitted to fit overhead electrification equipment, which was installed along its roof via nearly 7,000 holes driven into the ceiling.