TL;DR: David Silver, one of Britain’s most prominent AI researchers, is raising $1bn for London-based start-up Ineffable Intelligence in a deal led by Sequoia Capital at a $4bn valuation. If completed, it would be the largest seed round ever raised by a European start-up.

From AlphaGo to Superhuman Agents

David Silver, 49, spent more than a decade at Google DeepMind, where he helped develop AlphaGo and AlphaStar — AI systems that beat the world’s best players at Go and StarCraft. He also contributed to Google’s Gemini family of large language models before leaving late last year to launch Ineffable Intelligence.

The London-based company plans to build on Silver’s expertise in reinforcement learning, where AI systems improve through interaction with their environment rather than simply training on internet text. In a 2025 paper co-authored with Richard Sutton, Silver predicted that experience-based learning would “ultimately dwarf the scale of human data used in today’s systems.”

A Fiercely Competitive Fundraise

Sequoia Capital is leading the round, with managing partner Alfred Lin and partner Sonya Huang reportedly flying to London to meet Silver. Nvidia, Google and Microsoft are also in talks to invest, though negotiations remain ongoing and final terms could change.

The deal reflects a broader pattern of top AI researchers commanding enormous valuations for untested ventures. Former OpenAI executives Ilya Sutskever and Mira Murati have raised billions since leaving the ChatGPT maker in 2024. Meta’s former chief AI scientist Yann LeCun is raising roughly €500mn for his own project, AMI Labs.

Half of the $469bn invested by venture capitalists globally last year went to AI companies, according to CB Insights.

Looking Forward

Silver’s bet on reinforcement learning and experience-based training represents a distinct approach from the text-heavy training methods used by most current AI models. If Ineffable Intelligence can deliver on its promise of “superhuman capabilities” through experiential learning, it could shift how the next generation of AI agents is built — with particular implications for UK businesses watching London’s growing status as a global AI research hub.