The magistrates fined Hildreth �500

Adam Hildreth, 18, who is managing director of games and chat website Dubit, provided a positive blood test after he crashed his car following a night out with friends in February.

He told Leeds Magistrates' Court he believed he was capable of driving and was unaware that he had drunk five double vodka and cokes bought for him by a friend, thinking he had had just coke.

Hildreth, who was ranked fourth on a Sunday Times rich list of under 21-year-olds, said his stockbroker friend Chris Thorold bought him the drinks in city centre bar Northern Light despite being aware that he did not want to drink.

Punched in stomach

He said: "I felt fine. I didn't feel affected by alcohol. I wasn't aware that I had been drinking alcohol at Northern Light otherwise I would have mentioned it to someone."

Hildreth left the bar alone following an altercation in which he was punched in the stomach by a man at the bar and took a taxi to another friend's house, where he had left his car.

He then began to drive home in foggy conditions, believing that he had only drunk two pints of beer earlier in the evening, but crashed his Peugeot 206 into an embankment at a T-junction, leaving him concussed and with a broken nose.

He was taken to hospital where he had a blood test which showed 134mg of alcohol in 100ml of blood. The legal limit for driving is 80mg.

Fine and costs

Mr Thorold, 18, told the court that he had bought Hildreth alcohol even though he had asked him for a soft drink.

He said: "We didn't realise he would be driving or anything, we just wanted to liven him up a bit."

Chairman of the bench Michael Jones said the court accepted Hildreth's argument that his drinks had been laced with alcohol and that he was not aware that his abilities had been impaired.

Hildreth was fined �500 and ordered to pay �40 costs.