The Kilsby Tunnel is a railway tunnel on the West Coast Mainline railway in England. It was designed and engineered by Robert Stephenson.
The tunnel is located near the village of Kilsby in Northamptonshire roughly 5 miles (8 km) southeast of Rugby. The tunnel is 2,432 yards (2,223 metres) long.
The tunnel was opened in 1838 as a part of the London and Birmingham Railway. At the time of its opening, Kilsby tunnel was the longest tunnel in the world, and is today the 18th longest tunnel on the British railway system.
The tunnel took far longer, and cost far more money to build than had been anticipated. This was because the tunnel builders encountered unexpected quicksand which trial borings into the hill had not revealed. The excess water from the quicksand had to be pumped out, a process which took several years.
The length of time it took to build the tunnel delayed the opening of the London and Birmingham Railway.
It took three years, and cost £320,000 to build (three times the original estimate).
