A slew of U.S. Big Tech and AI companies are racing to expand in London as they look to take advantage of the city's deep talent pools amid a push to develop and commercialize frontier tech.Anthropic and OpenAI both announced they'd taken up larger office spaces in the U.K. capital in recent months. Vibe coding platform Cursor unveiled plans this week to open a London headquarters this summer and Google said it will begin moving teams into a new 11-storey building in Kings Cross in the coming months. Other key U.S. software players, such as Databricks and Salesforce, are also upping headcount or expanding their campuses in the city. Elsewhere, electric vehicle company Rivian and Palantir said in the second half of 2025 they'd also be growing in London."It's all about talent," Mike Wiseman, head of campuses at British Land, told CNBC. "London has built a deep and mature technology ecosystem over many years, and if you're looking to scale a business internationally, it's one of the few markets globally that can support that level of growth."Deep talent poolsAfter a quiet post-pandemic period, demand from tech companies has returned in London, Wiseman said. That's being driven by a "new generation" of companies that weren't on the radar a few years ago. Growth in the global AI sector has been fuelled by record funding figures over the past couple of years, as investors have rushed to back companies developing the tech. Startups globally have raised $392.1 billion so far this year, according to Dealroom, already dwarfing the previous record year of 2025, when companies secured $215.9 billion. London has emerged as one of the "deepest" pools of frontier AI talent outside of the U.S., Frederic Groussolles, partner at executive search firm Heidrick & Struggles, told CNBC."A decade of investment anchored by DeepMind, major research labs and leading universities has created a mature talent base spanning AI research, engineering and commercial leadership."Founded in 2010 in London, DeepMind was acquired by Google in 2014, but maintained a large team in the U.K. capital. Google DeepMind has since been behind the tech giant's Gemini models alongside a number of AI breakthroughs. watch nowWhen announcing Anthropic's London expansion in April, which saw it secure office space for 800 people — roughly four times its headcount in the city — head of EMEA north Pip White specifically flagged the "exceptional pool of AI talent" as a key driver of the move.Anthropic's new office space will be located in the Knowledge Quarter area of London, home to a slew of AI companies including OpenAI, Google DeepMind, Meta, Synthesia and Wayve.London is also one of the world's principal financial centers, Groussolles added, giving companies "ready access to venture, growth equity and corporate development networks."All of this activity in the London market from often hugely well-funded U.S. tech companies is putting pressure on local startups and making hiring top talent harder, said Dan Hyde, executive chair and founder at executive search firm Erevena. "These [U.S] companies are in a position to offer attractive packages (cash and equity) and meaningful work. Lots of people want to work for those companies."ChallengesSpace is a significant constraint for London's tech sector."The biggest structural challenge in London at the moment is supply," said Wiseman. "There is a well-documented shortage of high-quality office space coming through over the next few years, particularly in core locations, and that is likely to continue until 2030."British Land estimates that across London, there is a 10.4 meter square foot shortfall of new or substantially refurbished space to 2030.The shortage is being driven by the hypergrowth AI companies competing with more traditional finance and professional services firms for the same limited stock of top offices, added Groussolles.Beyond office space, there are concerns emerging around whether the infrastructure needed to support employees and rapidly increasing compute demands continues to match the pace of growth."The bigger issue is whether we continue investing in the infrastructure that supports growth, talent, power, housing, transport and compute," said Ziv Reichert, partner at London-based VC firm LocalGlobe. "Talent brought the labs to London, but keeping them here will depend on whether the UK builds the infrastructure around them," he added. "Compute, energy and capital matter just as much as researchers."