Moment David Cameron became a victim of crime

He had chained up his bike inPortobello Road, less than a mile from his home, as he went into a supermarket to buy salad for dinner.

However, when he returned five minutes later, the bike was gone. Mr Cameron had chained it to a 2ft bollard, allowing thieves to lift both the bicycle and the lock clear.

The moment that the 41-year-old politician realised his mountain bike had gone missing was captured on camera by a reader.

Today Mr Cameron said that he had reported the theft to the police but was not "holding his breath" for its return - nearly 20,000 bikes are stolen in London every year.

He added: "I was cycling home and stopped to pick up some things for supper. I chained the bike through the wheel then put it around one of those bollard things. I have reported it using the police's new online facility but I'm not expecting to get it back any time soon."

The bike is the one Mr Cameron regularly uses to cycle from his home to the House of Commons.

He appealed to the thief to return it, saying: "If anyone has seen it I would very much like it back. To me it was absolutely priceless."

Mr Cameron searched for about 15 minutes, asking passers-by if they had seen anything.

One shop worker, who asked not to be named, said the Tory leader at first could not believe he had been the victim of petty crime. He said: "He chained his bike to one of the bollards. There had been a couple of kids hanging around. They noticed he had chained it to a short bollard and they just picked it up and ran off.

"He was going up and down Portobello Road. He said, 'I am sure I chained my bike here and it is not here. I left it for five minutes - how can it be gone?' To start with he was not sure whether he had just left it somewhere else then after a few minutes he realised it was stolen.

"He was embarrassed and a bit annoyed. He was going round talking to people asking them if they had seen it - most people didn't recognise him."

At one point the Tory leader asked two men outside a betting shop in a desperate attempt to recover his bike. The shop worker added: "He was a bit cheesed off. One man asked if he could have his picture taken with him and he just said, 'Not now'."

The theft happened outside the Portobello Road branch of Tesco at about 6.30pm yesterday.

A Conservative spokesman said today: "Obviously David is quite hacked off by the theft of his bike, especially having locked it up. Unfortunately these kinds of incidents affect everybody and he is just going to take it on the chin and deal with it."