Sequoia and Nvidia Back AI Startup at $5.1B Valuation

David Silver left Google DeepMind in late 2025 after spending over a decade shaping the modern AI landscape through his work on AlphaGo, AlphaZero, AlphaStar, and contributions to Gemini. His new venture, Ineffable Intelligence, was incorporated in November 2025 and currently has no product, no revenue, and no public roadmap. What it does have is a bold thesis and a founder whose track record alone convinced investors to bet a billion dollars on conviction.

The London-based AI startup has secured backing from Sequoia Capital and Nvidia at a staggering $5.1 billion valuation. The funding round, among the largest ever for a startup at such an early stage, was led by Sequoia. Managing partner Alfred Lin and partner Sonya Huang personally flew to London to meet Silver and secure the deal. Nvidia’s venture arm contributed at least $250 million. The financing values a company founded just months ago, with no commercial output, at more than five billion dollars.

Silver’s decade-plus at Google DeepMind produced a series of landmark achievements. AlphaGo, released in 2016, became the first AI to defeat a professional Go player without a handicap. In Seoul, it beat 18-time world champion Lee Sedol 4-1 in a match watched by 200 million people across Asia. That moment resonated deeply in AI culture, triggering Marc Andreessen’s famous “Sputnik moment” description, catalyzing a wave of deep learning investment, and providing the foundation for Demis Hassabis to later receive the Nobel Prize in Chemistry for AlphaFold.

Silver then created AlphaZero, which mastered Go, Chess, and Shogi through pure self-play, without any human data. It was the first demonstration that a single reinforcement learning system could achieve superhuman performance across multiple complex games simultaneously. AlphaStar followed, reaching grandmaster-level performance in StarCraft II against professional players.

Ineffable Intelligence’s thesis directly challenges the prevailing AI development paradigm. In a 2025 paper co-authored with Richard Sutton, the University of Alberta researcher widely regarded as the father of reinforcement learning, Silver argues that large language models are fundamentally limited because they learn exclusively from human-generated data. They can synthesize, extend, and remix existing knowledge, but they cannot discover something genuinely new. Reinforcement learning, by contrast, allows an AI to learn from interaction with its environment, through trial, error, and self-play, producing strategies and insights no human has conceived. AlphaGo’s famous Move 37 in Game 2 against Lee Sedol was not in any human game record; it was discovered by a machine reasoning beyond human intuition. Silver is betting that scaling this approach is the path to superintelligence.

The valuation context is instructive. Ilya Sutskever, former Chief Scientist at OpenAI, left in 2024 to found Safe Superintelligence and raised $3 billion at a valuation reaching $32 billion by April 2025, also for a company with no product. Mira Murati, former CTO at OpenAI, founded Thinking Machines Lab and signed a multibillion-dollar cloud infrastructure agreement with Google. Meta’s former Chief AI Scientist Yann LeCun is raising approximately €500 million for AMI Labs. The pattern is clear: the AI investment market in 2025-26 is not valuing current capabilities. It is valuing the credibility of the researcher, the tractability of the thesis, and the track record of the team as a signal of the probability of a future breakthrough. By that metric, Silver, who built three of the most celebrated AI systems in history, commands a premium.

Ineffable Intelligence was incorporated in November 2025, with Silver appointed director in January 2026. The company is based in London, a location Silver deliberately chose. The UK is home to Google DeepMind’s headquarters, a deep academic pipeline from UCL and Oxford, and a growing density of frontier AI researchers who have left the major labs. Silver himself remains a professor at University College London. The $5.1 billion valuation makes Ineffable Intelligence immediately one of the most valuable pre-product AI startups in Europe.

The round was reported in February 2026 as being at approximately $4 billion pre-money; Monday’s Bloomberg valuation of $5.1 billion likely reflects the post-money figure after the capital injection, or an updated final close figure. The February reporting noted that Nvidia, Google, and Microsoft were in talks to participate; Monday’s confirmed deal has Sequoia and Nvidia as the confirmed investors.

Critics of Silver’s thesis are not silent. Reinforcement learning has achieved spectacular results in constrained domains with clear win conditions, such as Go, Chess, and StarCraft, but has historically struggled in open-ended real-world environments where the reward signal is ambiguous. How do you define “winning” when the goal is general intelligence? What prevents the system from optimizing for an unexpected proxy reward rather than the intended capability? These are not merely technical questions; they are the central unsolved problems of AI safety. Silver’s claim is that scaling the approach and applying it to open-ended research tasks rather than games will unlock qualitatively different capabilities. That claim is untested. Investors are paying $5.1 billion for the possibility that it is correct.