U.K.-based artificial intelligence startup Ineffable Intelligence raised $1.1 billion in new funding, putting the company's valuation at $5.1 billion.

The AI lab, founded by former DeepMind researcher David Silver, aims to build a "superlearner" using reinforcement learning. The system acquires abilities through experimentation rather than training on human-produced examples, its website states.

The funding round was led by Sequoia Capital and Lightspeed Venture Partners. Major investors include Index Ventures, Google, Nvidia, the British Business Bank, and Sovereign AI, the U.K.'s new state-backed AI venture fund, Wired reported.

Silver is a professor at University College London. He also previously ran DeepMind's reinforcement learning group for more than a decade. During that period, he worked on systems that focused on building reinforcement learning and co-led projects that played Atai games directly from pixels.

Former DeepMind employees Wojciech Czarnecki, Lasse Espeholt, and Junhyuk Oh have also joined Ineffable's executive team, according to LinkedIn.

Silver also described the venture as "his life's work" in a personal note posted to the company's blog. He recently told Wired that "any money” he makes from Ineffable will go to “high-impact” charities.

Ballooning AI Valuations

Ineffable Labs’ $5 billion valuation joins other AI startups that have quickly scaled as they compete for their place in the artificial intelligence market.

UK AI startups raised more than £6 billion in 2025, an 80% increase from 2024, capturing more than a third of all British venture capital—the highest share on record, AIfundingtracker reported. 

Notable firms that have led the way include Nscale, which was founded in 2024 and has a valuation of $14.6 billion. Key investors in the AI infrastructure hyperscaler include NVIDIA, SoftBank, Citadel, and Fidelity Management, among others.

Meanwhile, Eleven Labs' most recent Series D funding raised $500 million, which was led by Sequoia Capital. This puts the AI startup at an $11 billion valuation.

Key investors included Andreessen Horowitz, ICONIQ, Lightspeed Venture Partners, Evantic Capital, BOND, Smash Capital.

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