"It beggars belief" - that was the damning verdict of police officers after one driver was clocked at 79mph on the Oxford Eastern Bypass yesterday.

In just one hour of speed enforcement on the notorious stretch of the ring road - the first for seven years - 20 drivers were clocked well above the 50mph limit.

And some motorists were racing so fast they could face a £1,000 fine or even a ban.

Police mounted the mobile speed checks close to the site of the crash that claimed four young lives in May, 2005. Although speed was not a factor in that accident, it is a factor in 10 per cent of collisions on the road.

And within minutes of film rolling yesterday, the camera was clocking drivers exceeding the 57mph threshold.

The worst offenders in the first hour registered 79mph, 76mph and 73mph in the 50mph zone - fast enough to ensure a speedy journey straight to court.

Road safety officer for Thames Valley Police, Sgt Chris Appleby, said he was disappointed with the high speeds recorded.

He added: "We have signs, vehicle actuated signs that flash to tell you to do 50mph and they still come through at 70mph approaching a well-marked police van - it beggars belief really."

But he said the aim of yesterday's operation was to catch and educate drivers.

And he added enforcement would continue as long as it was needed.

Sgt Appleby said: "Today we are looking at raising awareness of the fact that this location has had a casualty problem and continues to do so."

"There are too many casualties here and we have got to reduce them."

He added: "We will keep sending this van out as long as it's needed. While there is a problem with speeding and collisions, we will keep coming. It's that simple."

Dan Campsall, of the Thames Valley Safer Roads Partnership, said the speeds clocked by some motorists yesterday were simply unacceptable.

He said the road's safety record spoke for itself.

He said: "Sixty collisions over three years is high for a road of this sort.

"Ten per cent of those are people doing over the speed limit."

But asked whether action had been taken soon enough following the tragedy in 2005, he said the action was not in response to one accident but aimed at tackling the overall problem.