Riding the investment wave, a crop of foreign AI firms - including Canada's Cohere and U.S.-based Anthropic and OpenAI - opened offices in Europe last year, adding to pressure on tech companies already trying to attract and retain talent in the region.

Founded in 2010 and acquired by Google in 2014, London-based DeepMind made its name applying AI to everything from board games to structural biology.

Now the firm faces a host of well-funded rivals flooding its territory, while a growing number of its employees have quit to launch their ventures.

Recent high-profile exits include co-founder Mustafa Suleyman, who left to set up California-based Inflection AI alongside LinkedIn billionaire Reid Hoffman, and research scientist Arthur Mensch, now CEO of Mistral AI. Both companies have received multi-billion dollar valuations in the short time they have been active.

In an apparent effort to discourage staff from joining other companies or starting their own, DeepMind gave a handful of senior researchers access to restricted stock, worth millions of dollars, earlier this year, according to a source familiar with the matter.