Julian Dunkerton has already seen the course of his life change dramatically, in his rise from humble market stall trader to fashion mogul with A-list celebrities DJ-ing at his wedding.

Now the multimillionaire founder of the Superdry label hopes to play a role in changing the future of the nation. His £1m gift to the People’s Vote campaign, demanding a new referendum on the terms of Britain’s EU exit, catapults him into a small group of people to make six-figure political donations in Britain. Such is the toxicity of the Brexit debate that finding business figures willing to enter the fray has been a difficult task for those wanting to revisit the decision, making Dunkerton’s public donation a significant moment.

Dunkerton, 53, began his career running a stall in Cheltenham in the 1980s before starting up the Superdry label with the designer James Holder in 2003. The brand’s first shop opened in Covent Garden in London in 2004 and there are now more than 500 outlets in 46 countries. Dunkerton is said to have a personal fortune of £441m.

At his marriage to the designer Jade Holland Cooper last weekend, the actor Idris Elba was spotted DJ-ing alongside the musician Craig David. Dunkerton has described operating on a diet of nine coffee shots a day and stubbornly refuses to own a smartphone. He still lives outside Cheltenham and can sometimes be spotted fishing on the River Avon.

Dunkerton’s investment in the People’s Vote campaign comes after he took a step away from Superdry earlier this year. He has since sold off a portion of his shares, but still retains a major stake. He has also transferred more than £1m in shares to the Blue Marine Foundation, a charity focusing on overfishing and biodiversity. He has invested in a number of restaurants, hotels and gastropubs. In 2014 he also took over the cider business established by his parents Ivor and Susie.

He aired his concerns about Brexit in the run-up to the 2016 referendum, publicly criticising Boris Johnson for opting to lead the Leave campaign and warning that exiting the bloc would be a disaster.

While he has not made a political donation in the past, he has spoken of coming from a leftwing background and having a “deep-seated desire to do the right thing”. He said earlier this year: “I was a Labour supporter in the 1980s but today I’m non-party political and a strict Remainer.” He has now proved it with his wallet.