Gerrards Cross Tunnel is a 310-metre-long (340 yd) railway tunnel in Gerrards Cross, Buckinghamshire, on the Chiltern Main Line, next to the railway station. The purpose of the tunnel was to enable a new Tesco supermarket to be built over the railway line. Plans were initially met with anger by local residents, and the council refused planning permission, but this decision was overturned by Secretary of State for the Environment, Transport and the Regions John Prescott. During construction of the tunnel, it partially collapsed on 30 June 2005. No-one was injured in the accident, although a train heading towards the tunnel when it collapsed had to perform an emergency stop. Early reports suspected the cause was the backfilling operation. An initial freedom of information request on 10 December 2020 was denied; however, a later request in 2022 was successful, and confirmed the cause of collapse to be the backfilling operation. Despite the incident, the construction continued in 2007 with different contractors building the tunnel. The store opened in November 2010, fourteen years after the project was commissioned.
Background Tesco, the third largest retailer in the world measured by revenues and the second largest measured by profits first proposed a store on the site in 1996. The local council also objected to the development and a public inquiry endorsed this decision. In July 1998, however, Deputy Prime Minister John Prescott overturned the council's ruling on the basis of the recommendations of an independent planning inspector. Due to a lack of space in the area, Tesco had proposed building over the railway line, which would free up a large area of land suitable for the development. The work was let under a design and build contract to Jackson Civil Engineering, who announced the store would be designed by White Young Green, and specialist supplier Reinforced Earth Company. Work started on site in early 2003. At the time Jackson Civil Engineering were part of the Peterhouse Group, which was subsequently bought by Babcock International Group in 2004, after the Jackson Civil Engineering division had been sold in a management buyout. Babcock were still subject to the parent company guarantee that Peterhouse Group had entered into when the contract to build the tunnel was let. The design used precast concrete sections, each of which made up half of a three-pinned arch. These segments were connected to each other at the middle of the arch, and material then built back up over the arch, known as backfilling. The method of construction was not unique. "There are eight tunnels like this in Britain," said James Ford of Chiltern Railways, "and something like a thousand worldwide." At the time of collapse, construction work on the tunnel segments had finished, and the backfilling operation was taking place. The foundations had been built and the steel frame of the supermarket erected.
Collapse
At 7.34pm on 30 June 2005, 30 metres (33 yards) of the 320 metre (350 yard) tunnel collapsed. At the time, there were no trains passing through the tunnel, although one train, heading west towards High Wycombe, had to make an emergency stop. The train had passed through Denham Golf Club station, the last stop before Gerrards Cross, before the driver was warned by radio. He reversed the train to Denham Golf Club, where all passengers were let off. Additionally, a London-bound train was standing at the eastbound platform at Gerrards Cross waiting to depart. The driver of this train had just set the train in motion when he saw the collapse, stopped his train using the emergency brake, and informed the railway signallers by radio; they in turn stopped other trains. There were no casualties as a result of the incident. One witness told a news channel that he was parking his car when he heard "what sounded like a clap of thunder - I thought it was an earthquake. I saw the tunnel falling on to the rail track." Reg Whittome, chairman of the Marylebone Travellers' Association and the Chiltern Railway Passenger Board, said after the incident that, had a train been going through the tunnel when it collapsed, there would have been an "almighty tragedy". He added: "Had it been during the rush hour, hundreds could have been killed."
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