Ineffable Intelligence, a London-based AI lab founded five months ago, launched on April 27 with a $1.1 billion seed round — the largest in European startup history — at a $5.1 billion valuation. The company has yet to release a product, generate revenue, or publish a public roadmap. So far, all it has is David Silver.
Silver, a professor at University College London and the former head of reinforcement learning at DeepMind, founded Ineffable in November 2025. He spent more than a decade at DeepMind, where he led the team behind AlphaGo and AlphaZero — programs that mastered the game of Go and chess by playing millions of games against themselves rather than learning from human examples.
Ineffable’s thesis is a direct extension of that work: build a “superlearner” capable of discovering knowledge entirely through its own experience, without relying on human-generated training data. The bet is that reinforcement learning, applied at sufficient scale, produces a fundamentally different and more powerful kind of AI than the large language model paradigm currently dominating the industry.
Sequoia and Lightspeed co-led the round, with participation from Nvidia (Nasdaq: NVDA), Google (Nasdaq: GOOGL), Index Ventures, DST Global, and the UK government’s Sovereign AI Fund and British Business Bank. Nvidia’s venture arm contributed at least $250 million.
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UK Science and Technology Secretary Liz Kendall backed the raise publicly, saying the investment would help ensure “the UK isn’t just an AI taker but an AI maker.”
Silver has also pledged to donate 100% of his personal equity gains from Ineffable to high-impact charities via Founders Pledge — described by the organization as the largest commitment in its history, likely to amount to multiple billions if the company reaches its ambitions.
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