A dotcom analyst who was earning £1m at the age of 30 was ordered yesterday to repay a £250,000 bonus - plus £10,000 in interest - he received by mistake.

The court of appeal overturned a lower court's ruling that allowed Gareth Price-Jones to keep the bonus paid to him by German-owned Commerzbank.

Mr Price-Jones, now 33, was hired by Commerzbank from Schroders in April 2000 to head its internet research team at the height of the dotcom boom but was made redundant in November 2001.

The court of appeal judges overruled a decision a year ago by a deputy high court judge that Mr Price-Jones was entitled to keep the bonus.

The confusion arose over a promise by Commerzbank to give Mr Price-Jones a guaranteed bonus of £250,000 a year. In June 2000, he received a letter putting his bonus at £265,000. He believed this to be in addition to the guaranteed bonus, but Commerzbank had argued that it meant to give only an additional £15,000.

The deputy judge in the lower court ruled that, even though Commerzbank had meant to pay him only an extra £15,000, Mr Price-Jones was entitled to the total of £515,000 because of contracts he had signed.

The court of appeal judges ruled yesterday that if the bank had intended to increase the guaranteed bonus to £515,000 it would have made it plain in the letter it sent to Mr Price-Jones.

In the court of appeal yesterday, Lord Justice Mummery said Mr Price-Jones had been "unjustly enriched" as a result of the payment.

"A just man would recognise that it was unjust to keep it and that he ought to repay it," said Lord Justice Mummery, who presided over the case with Lord Justice Sedley and Mr Justice Munby.

"The payment was a mistake. He has still got the money. There is no obstacle to repaying it," Lord Justice Mummery said.

Mr Price-Jones was not immediately available for comment yesterday. Commerzbank said it was "very pleased" with the result of the appeal.

The case is one of the few that helps lift the veil of secrecy on pay levels in the City, particularly during the dotcom boom when investment banks raced to hire individuals with expertise in the emerging market.

Since the end of the boom, guaranteed bonuses have been less common, according to City insiders, and many of the individuals hired to specialise in the internet have lost their jobs.