The Environment Agency alleged that T Clarke (Midlands) Ltd, a London-based contractor to the Ministry of Defence, was responsible for a 36,000 gallon leak of fuel which had been destined for aircraft.

The company is on trial at Ipswich Crown Court where it has denied a charge of causing poisonous or noxious matter to enter controlled waters contrary to the Water Resources Act, on April 20, 2007.

An official from the government organisation responsible for maintaining infrastructure at RAF Mildenhall this week told the court how the full extent of what happened to the fuel pipeline was uncovered.

Paul Newton-Griffith, from the Defence Estates organisation, said that when investigatory trenches were dug, workers found the shaft of a drilling machine embedded in the pipe with fuel leaking out around it.

The extent of the fuel leak was limited, to a degree, by switching off valves to isolate the damaged section of pipe, said Mr Newton-Griffith. However, some of jet aircraft fuel did continue to leak into the trench and special matting and a drip tray was deployed to catch as much of it as possible.

Two trenches – each around four metres deep – were dug within five days of evidence of a leak from where drilling had been going on and where machinery had become stuck, said Mr Newton-Griffith.

He said that a permit to carry out the drilling work had been granted to T Clarke (Midlands) Ltd which would have been responsible for ensuring that the location of all potential underground hazards had been identified before work began.

The operation to remove the drill shaft from the pipeline was finally able to get underway on May 14 when engineers cut through the shaft.

Giving evidence, Mr Newton-Griffith said that while the operation was taking place, no representative of T Clarke (Midlands) Ltd asked to be present.

Sub-contractor Roy Clarke, who had been called in to carry out underground drilling work at the airbase by T Clarke (Midlands) Ltd, told the court that he could not recall the location of the fuel pipe being marked on the surface.

Mr Clarke, from Diss, who runs a business called Underground Solutions, said that other potential hazards, including three power cables serving landing lights, had been identified and marked with yellow paint by staff from T Clarke (Midlands) Ltd.

Using specialist machinery, Mr Clarke said he and his team began drilling operations until they broke the surface on the other side of the taxiway. It was only when they had changed to a larger boring tool and tried to pull the drill back towards them that it became apparent there was a problem.

However, said Mr Clarke, despite by his estimation the fuel pipe having been struck about 45 minutes into the drilling operation, he had not smelled or seen any evidence of a fuel leak.