Sir Terence Conran has successfully defended a High Court claim brought by restaurateur tycoon Des Gunewardena, who was seeking £3m in a bitter battle between the two former business partners.

Gunewardena claimed he had been “betrayed” by Sir Terence and accused the designer’s son, Jasper, of being involved in depriving him of a £3m stake in the Conran business.

Gunewardena claimed he was fired by Sir Terence’s company after giving body and soul to it for more than 20 years and being chief executive for 11 years. He complained that he was paid £1,254 for his stake in Conran Holdings Ltd after he was forced to sell his 7% stake back to the company when he was axed as a director in 2013.

Gunewardena, 59, joined Sir Terence’s business in 1991 when it had one restaurant, one shop and a design company. He said that together they turned Conran Holdings into an international dining and design empire that, at its peak, had 2,000 staff and a turnover of £120m.

But High Court judge Mr Justice Mann dismissed the claim on Tuesday, and said Gunewardena’s evidence was often “wishful thinking”.

“At best he has convinced himself that things had happened (or did not happen) because that is necessary for his case. In some instances I fear he was saying things that he knew to be untrue. I did not feel I could always rely on his evidence,” said the judge.

Mr Justice Mann added that Sir Terence was “physically frail but certainly not mentally frail”, and that his ability to remember details was “no worse than the failure of much younger witnesses”.

Gunewardena is understood to beconsidering an appeal.

A spokesperson for Gunewardena said: “Des stands by the case he brought and the evidence he gave. In his evidence Sir Terence Conran described Des as a man of integrity. This case was simply about Des receiving a fair price for shares he had acquired in a company that he had served for over two decades. Des is understandably disappointed by the judgment and is now considering an appeal.”