James Watt, the BrewDog founder who offloaded the debt-ridden "punk" brewer earlier this year, is facing complaints to the UK's data privacy watchdog over his surprise bid to buy the company back. The Guardian has learned that Watt's email campaign to thousands of former investors - dubbed "equity punks" - has raised eyebrows and GDPR concerns.

In March, BrewDog's brand, IP, UK breweries, and 11 bars were sold to US cannabis and drinks firm Tilray for £33 million, rendering the shares of over 200,000 crowdfunding investors worthless. On Wednesday, Watt announced a plan to reclaim the company via a new venture called Second Best, backed by 43,000 of those investors. The proposal involved contacting shareholders to offer them the "exact same stake in Second Best that you once held in BrewDog, for free."

Several recipients of Watt's email expressed confusion over how he obtained their contact details, sparking concerns about a potential breach of GDPR. Watt denied any wrongdoing, stating that the communication was sent "following legal advice, using lawfully obtained data, and in connection with their legitimate interests as shareholders." He did not explain how the data was obtained.

The Information Commissioner's Office (ICO), which regulates data privacy, is now considering complaints from former shareholders. Marc Knox, a former equity punk, said he initially laughed at the email but later wondered, "How has this joker got my details?"

The Guardian understands that neither Tilray nor AlixPartners, the administrator of the remainder of BrewDog, provided any such information to Watt. Ravi Naik, legal director at data protection specialist AWO, said the case raises significant questions, though a breach is not yet clear.

Tilray confirmed it did not acquire shareholder data as part of the acquisition and did not authorize any communications. The ICO declined to comment on individual cases.