A rowing coach was left unconscious with facial injuries after he tried to stop a thief escaping from police.

Rob Offord, 20, was left lying at Osney Lock, drifting in and out of consciousness with a broken nose.

Rob Offord and his girlfriend Rachel Dryer Mr Offord had tried to stop a man who smashed the rear windscreen of a blue Volvo Estate outside PC World in Botley Road, and stole a laptop from the back seat.

The thief was chased by police as he rode off on a silver mountain bike towards the city centre at 7pm on Tuesday.

He went down Ferry Hinksey Road before heading towards Osney Lock.

Mr Offord said: "I was opening the lock for a rowing crew and noticed a guy cycling towards the lock, then a police car pull up by the road. Two officers jumped out and started sprinting in the same direction.

"The cyclist had to slow down dramatically to get through the chicane at the lock.

"He came through slowly, then gathered his pace again and I tried to grab him. He came straight at me.

"He punched me and I fell to the ground. As a rowing coach, I am aware of the dangers of drowning, and I was just trying to get away from the water. He got me with a full pelt punch as he was cycling one handed."

Mr Offord, of Cowley Road, put himself in the recovery position and waved the police officers past in the hope they would be able to catch the thief.

He handed his mobile phone to two women who called for an ambulance, and gave him their jackets to rest his head on.

He said: "I was trying to hold my own head up because I didn't want the blood to drip back into my nose.

"The whole thing, from being punched, is a blur, I was going blank every so often and I don't remember half of it."

The police officers returned to the scene, checked Mr Offord was still breathing and carried out first aid.

An ambulance took Mr Offord, who has just finished a degree at Oxford Brookes University, to the John Radcliffe Hospital, where he was treated and released at about 12.30am.

Mr Offord, who has a part-time job as a hospital porter and security guard in his home town of Camberley in Surrey, said: "I felt a bit stupid for getting involved, but I was a citizen trying to stop a criminal getting away. At the same time I wasn't going to knock him off his bike and beat him up -- I don't want to be a vigilante.

"I'm very lucky I don't have a broken skull and was lucky he didn't have a knife. The police have stab proof vests and CS gas, I don't."

Det Sgt Tony Lees, of the Oxford police autocrime team, said: "What Mr Offord did was an incredibly brave and courageous thing."

The thief is white, aged between 25 and 30, of medium build, clean shaven and has blonde hair which is shaved at the back with a small fringe.

He was wearing a navy shell-suit with a white shirt underneath and was carrying a rucksack.

Call Pc Lees on 08458 505505 or Crimestoppers on 0800 555111.