Billionaire Mike Ashley enjoyed a rare bit of good news this morning as it emerged that the reclusive Sports Direct boss has turned a quick £29m profit on his stake in Adidas.

Mr Ashley spent almost £200m of the £930m he raised through the February float of his sportswear empire buying shares in the German sports group. But, according to a report in today's Financial Times, he held the shares for just eight weeks before selling at a substantial profit.

Boosted by his share purchases, Adidas shares jumped from €39.18 in March to reach €45.47 last month.

As the shares were a personal holding, the profit goes to Mr Ashley. But there was some relief for shareholders in Sports Direct today as the shares, which have slumped in recent weeks, rebounded by more than 7%, jumping 14.5p to 205p.

However, this still leaves them almost a third lower than the 300p at which they floated just three months ago. They fell to a new low of 183p at one stage yesterday.

The maverick Mr Ashley has seen his credibility severely dented in the City because of his uncommunicative and unconventional approach to business.

His reputation was further tarnished last week as David Richardson abruptly quit as chairman of the group. The former Whitbread finance director had been brought in ahead of the float in an effort to ease City concerns over the way the business was run.

Investors have also been highly critical of Mr Ashley's £133m bid for Newcastle United football club, although, like the Adidas stake, the Newcastle move is being funded from Mr Ashley's personal resources.

Shareholders in Sports Direct were further alarmed over the weekend as an extraordinary story emerged of how Mr Ashley settled a dispute over a £200,000 legal bill associated with the group's flotation by a game of spoof.

The pub guessing game was suggested by the billionaire and played with Merrill Lynch investment banker Simon Mackenzie-Smith, who apparently won.

Mr Ashley, reckoned to be the 25th richest person in Britain, sold 43% of Sports Direct during the float and remains the controlling shareholder.

Retail analyst Andrew Wade at Seymour Pierce was impressed by Mr Ashley's quick turn on the Adidas stake: "Say what you like, but he does know the sports market. He did a similar thing with JJB shares."

While Mr Wade believes there "is still a growth story with Sports Direct, the lack of credibility and visibility makes it very hard to recommend the stock."