Thursday, June 30, 2005 started off like any other day for the people in Gerrards Cross. A controversial new Tesco store was being built in the centre of the village, over the railway line linking it with London Marylebone, and despite years of opposition to the plans from people living nearby and the district council, work on the supermarket was well under way.

Due to a lack of space in the area for a new store, Tesco had proposed an innovative concept involving building over the railway line, using large concrete sections to create a tunnel through which trains could travel. On the top of the new tunnel, tonnes of soil would be used to provide the land which the store would be built on.

Construction had reached a stage at which the tunnel segments had been finished, foundations were in place, and the steel frame of the new Tesco had been erected.

“There had been a lot of objection,” says parish councillor Mike Lawson, who still lives in the village, “but it had reached a stage where the majority of people had accepted it.

“The work was going ahead and the project was starting to take shape. No one had any reason to think that something would happen to change that.”

CREDIT GUY GORTON: The Tesco tunnel in the aftermath of the collapse.

Shortly after 7.30pm that evening, however, something did happen – 30 metres of the 320 metre long tunnel collapsed onto the railway line below, bringing with it 25,000 tonnes of earth and rubble.

A witness told the BBC at the time that 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”.

The margins by which tragedy was averted were incredibly narrow. A train had just begun to move away from Gerrards Cross station on its way to the capital when its driver saw the collapse, stopped his train using his emergency break and informed radio signallers who passed the message on to other trains.

Commuters on their way from London on a west bound train heading to High Wycombe were evacuated, having just passed through Denham Golf Club, the last stop before Gerrards Cross.

“The fact that no one was hurt was remarkable,” says Ros Hurn, who had been campaigning against the store being built. “We are talking about a couple of minutes between it happening and a major tragedy.

“The train driver at Gerrards Cross was incredibly quick thinking and saved the lives of a lot of people.”

It is believed that the incident had been caused because of a combination of a flaw in the design of the arches used for the tunnel, as well as soil used for backfilling being unevenly distributed on the tunnel’s side sections. Heavy rainfall in the days leading up to the collapse could also have contributed to the accident.

“There was a feeling of great shock,” says Mr Lawson. “People were astounded by what had happened, and by how close we’d come to a major tragedy in our village. The mess it created was incredible.”

CREDIT GUY GORTON: The Tesco tunnel in the aftermath of the collapse.

In the following weeks, trains were diverted around Gerrards Cross, with replacement bus services being put in place, and serious doubt was cast on the store’s future, with MP Dominic Grieve lending his voice to calls for it to be scrapped.

Mrs Hurn says: “It gave the campaign new hope – there was a time when people thought it wouldn’t end up going ahead.”

However, in 2006, Tesco appointed a new contractor to redesign the project, and the store finally opened its doors in 2010, five years later than planned.

During construction, the supermarket giant offered Gerrards Cross Parish Council £100,000 to spend on village projects as a goodwill gesture for the disruption that it caused.

“I think broadly speaking, Tesco has been a good addition to the village,” says Mr Lawson. “It’s created new parking, it’s brought people here and it’s joined the two parts of Packhorse Road together.

“There are still a few diehard people who are anti it, but now that it’s been up and running for a few years, I think it’s generally had a positive impact. But it did take a long time, with a lot of unexpected drama, for us to get to this stage.”