Vital witnesses to the crash which killed TT race champion David Jefferies were not quizzed about the accident, it has been claimed.

An inquest into the 30-year-old top motorcyclist's death was opened on the Isle of Man yesterday.

Mr Jefferies, of Baildon, suffered multiple injuries when his 1000cc Suzuki machine crashed into a telegraph pole during a practice lap of the TT circuit on May 29. He died at the scene and his body was later identified by his mother, Pauline, who acts at a timekeeper at the TT and who was six miles away on the race grandstand when the accident happened.

Advocate Peter Saunders, who appeared at the inquest on behalf of TAS Suzuki, which Mr Jefferies was part of, said he wanted to produce evidence from five TT competitors which could help explain why the experienced rider crashed at Crosby.

He said witness statements, which could show there was oil on the course, had not been gathered from the riders.

There has been massive speculation about the cause of the tragedy, including reports that oil may have been left on the road by another machine.

There was also speculation that a vehicle has pulled on to the circuit just before the accident, although Isle of Man Coroner Michael Moyle confirmed at yesterday's hearing that the theory of a third party coming onto the circuit could be discounted.

He said the cause of the accident was likely to be oil on the circuit or a misjudgement by the rider.

The hearing was adjourned after Mr Saunders, who met his clients just 15 minutes before it started, said he wanted four drivers who were at the scene and a rider who followed a bike which broke down further along the course to be interviewed.

"They can tell us whether there was oil on the road," he told the inquest. "I would contend this accident was down to a spillage of oil on the road and not a question of the skill of the rider."

Before adjourning the case to allow time for Mr Saunders to gather his evidence, the coroner read out statements from two German TT fans - Martin Holtkamp and Berntd Preiss - who watched the practice session from Crosby Post Office, near the crash scene.

Both saw a bike pulled in by the post office, with steam coming from it. They also said there was a "small patch" of liquid on the road.

Neither of them saw Mr Jefferies actually crash.

Mr Moyle said the Isle of Man did not operate a "secret society" and said any information which could "usefully help us get to the bottom of this accident" should be included at the resumed hearing.

There were two videos taken at the scene which would form part of the evidence. Both showed the aftermath of the crash, but not the impact itself.