Air shaft in the Kilsby Tunnel, illustrated in an 1852 railway publication.
|Operator||West Coast Main Line|
|No. of tracks||Two|
The tunnel took far longer, and cost far more money to build than had been anticipated. This was because the tunnel roof collapsed and the tunnel flooded unexpectedly due to 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 eight months. Similar problems were encountered with nearby Blisworth tunnel on the Grand Union Canal a few decades earlier.
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 (£23,758,000 in 2005 pounds).