Mishcon de Reya has lost a High Court case against Sports Direct owner Mike Ashley, disputing an alleged £15m business promise made at a pub.

Former Merrill Lynch investment banker Jeff Blue claimed that Ashley had promised him £15m in a pub discussion if the retailer’s share price doubled within three years. At the time in January 2013, shares in Sports Direct were trading at around £4 per share.

Fountain Court Chambers’ Jeffrey Chapman QC and Simon Atrill were instructed by Mishcon de Reya’s Richard Leedham for Blue, while One Essex Court’s David Cavender QC and Tamara Kagan were instructed by RPC head of commercial, IP, tech and media Jeremy Drew for Ashley.

Mr Justice Leggatt said in his High Court decision that the fact that Blue had convinced himself that Ashley’s offer was a serious one “shows only that the human capacity for wishful thinking knows few bounds”.

Ashley gave evidence during the trial saying he “recalls talking about the Sports Direct share price and how much he would be worth at different hypothetical share prices” but does not recall any discussion of paying Blue a sum of money if the Sports Direct share price reached £8 per share.

Ashley also claimed that he was trying to get drunk that evening, that Espirito Santo Investment Bank head of market Simon McEvoy, who was also present, “stood at the bar and ‘kept the pints coming like machine guns'”, that they must have had four or five rounds in the first hour and that he (Ashley) was making Blue keep up with the others.

It was argued on behalf of Blue that, while this might be true in the case of an ordinary businessman, Ashley is not an ordinary businessman but is someone who adopts an “unorthodox approach to taking business decisions in informal settings while consuming substantial amounts of alcohol”. In particular, Blue relied on the fact that, at Sports Direct’s weekly senior management meetings he had witnessed Ashley (and others) drinking alcohol, sometimes allegedly in copious quantities.

Mr Justice Leggatt said in his judgment: “I see no reason to doubt the evidence (…) that everyone was laughing during the conversation, nor the evidence of Mr Tracey that during the conversation Mr Blue had a big grin on his face and was looking ‘over the moon’.

“Mr Blue’s explanation for why he did not mention the subject to Mr Ashley until, on his evidence, late December 2013 is that he saw no need to do so because their agreement was clear and he trusted Mr Ashley to honour it. But that explanation does not stand a moment’s scrutiny.”

He continued: “Even if Mr Blue had believed that Mr Ashley was being serious, the circumstances in which the conversation took place – an informal meeting with Sports Direct’s new corporate brokers in a pub in which the drinks were flowing, people were laughing, and when Mr Blue (on his own admission) had been surprised when the idea of offering him an incentive had been discussed – would at the very least have signalled the need to get Mr Ashley’s confirmation of the arrangement in the light of day.”

Last year, The Lawyer reported that RPC slammed its client Sports Direct in a report heavily criticising working conditions at the retailer’s warehouses, two years after the company side-stepped an employment tribunal over zero-hours’ contracts.

The report, commissioned by Sports Direct and authored by the law firm, was published in response to allegations that the business had mistreated its staff through the use of zero hour contracts and had breached national minimum wage regulations.