Britain's fastest convicted speeder was jailed for 10 weeks yesterday after police caught him doing 172mph in a Porsche on a rural A-road.

Tim Brady's record speeding offence - nearly two and a half times the 70mph limit - was clocked by a constable holding a speed gun on the A420 near Abingdon in Oxfordshire. He became the fastest speeder ever caught by a British speed trap when he admitted one count of dangerous driving.

The 33-year-old, of Harrow, was driving a £98,000 3.6-litre Porsche 911 Turbo, taken from Helphire, his then workplace, a luxury car hire firm, Oxford Crown Court heard. Jailing Brady, Judge David Morton Jack said: "Your driving was criminally self-indulgent and utterly thoughtless of the danger you might be creating for the innocent."

The previous record for the fastest car clocked by a speed camera to result in a conviction was 156mph - in 2003 by Aberdeen car dealer Jason McAllister on the A90 between Aberdeen and Dundee. The court heard Brady nagged his boss Bill Maclachan the previous day to let him take the sports car for a spin but was repeatedly told no.

But Brady returned the next day, his day off, and took the vehicle out, claiming Mr Maclachan "did not say no to that idea".

John Reilly, for Brady, said in mitigation that although he had been refused permission to drive the vehicle, employees at the firm often drove such cars.

"It was not company policy but sometimes blind eyes were turned," he told the court.

Police were tending to another motorist who had been doing 115mph on the same stretch of road when Pc Peter Billingham clocked Brady with his speed gun.

When caught, Brady said: "Oh s***, oh s***, I've lost my job," the court heard.

A Porsche travelling at 77 metres per second needs 501 metres to stop. Brady, with a colleague on board, stopped in 681 metres, the car wobbling due to heavy braking.