The disused railway which runs eastwards through Keswick towards Penrith passes by a tunnel through a rocky spur just to the east of the town, immediately underneath the viaduct which carries the Keswick by-pass (A66).
The Bobbin Mill Tunnel was
originally one of the two tunnels on the Cockermouth, Keswick and Penrith
railway line and was dug through a spur on the banks of the river Greta. The
line was closed in 1972.
In 1977, the Greta viaduct on the Keswick By-pass was constructed over the River Greta at a higher level, spanning the spur through which the tunnel was built. It was voted "Best Concrete Engineering Structure of the Century" by "Concrete" magazine.
Subsequently a path was constructed along the line of the old railway line from Keswick as far as Threlkeld. It was thought that the integrity of the tunnel might have been compromised by the viaduct construction and it was sealed off so initially access between the town and the railway path to the east was by a precipitous climb and descent over the spur, immediately below the deck of the viaduct - difficult for walkers and nigh on impossible for cyclists. In 2001, Sustrans, with the aid of a volunteer workforce overcame this obstacle by building a boardwalk round the precipitous slopes of the spur, thereby opening up the disused railway to all comers. The path formed part of the C2C cycle route (National Cycle Network route 71) and was very popular with walkers and cyclists.
The walkway was destroyed by Storm Desmond in 2015
along with 200 metres of path and two bridges to the east of the tunnel with a
further bridge seriously damaged. A major reconstruction project was launched to
rebuild the path at a total cost of £7.9 million. During reconstruction, it was determined that the tunnel was safe after all and was
incorporated into the path.