Box Tunnel

Box Tunnel cuts through Box Hill on the Great Western Main Line between Bath and Chippenham. When it opened in 1841 it became the world’s longest railway tunnel at nearly two miles. Isambard Kingdom Brunel designed the straight tunnel with a steady one-in-a-hundred slope down from the eastern end. The western entrance is a grand classical arch while the eastern end has a simpler brick face. During the Second World War the hillside was used to store ammunition in old mine workings. In the 2010s the track was lowered for planned electrification, though this work was later suspended. The tunnel’s construction between 1838 and 1841 was judged dangerous because of the mixed rock layers it had to pass through. Brunel sank eight deep shafts along the route to test the ground before work began. Contractors divided the job into six sections, each served by a large ventilation shaft up to 300 feet deep. Navvies used candles and explosives at a rate of one tonne of candles and an equal weight of gunpowder every week. About a hundred workers died during the three years of digging. Visitors today see the grand western portal near Box, Wiltshire, standing much higher than needed for trains. The eastern portal at Corsham is a modest brick face with stone dressings. Parts of the tunnel remain unlined, showing the raw rock walls. The track now sits lower than originally laid, leaving the tall entrance even more striking. The surrounding Box Hill landscape still carries scars from the stone quarries that once fed Bath’s builders. A raised loading platform built for wartime munitions can be glimpsed near the eastern end.