AlphaGo architect David Silver raises £880 million for Ineffable in UK record

London-based AI startup Ineffable Intelligence has secured a record-breaking $1.1 billion (£880 million) seed funding round, the largest ever raised by a European or UK company at the seed stage.

This puts its post-money valuation at $5.1 billion (£3.77 billion).

The announcement on Monday (27 April) marks a major milestone for UK AI innovation and comes just months after the company emerged from stealth.

The round was co-led by Sequoia Capital and Lightspeed Venture Partners, with participation from NVIDIA, Google, Index Ventures, DST Global, Evantic Capital, Flying Fish Ventures, EQT Ventures, BOND Capital, the UK Wellcome Trust, the British Business Bank, and the UK government’s Sovereign AI Fund, among others and strategic angels.

What does Ineffable do?

Ineffable Intelligence is the latest frontier AI company to receive backing through the UK government’s Sovereign AI Fund, which is designed to help the UK’s most promising AI startups grow, scale and succeed from Britain.

Founded by one of the world’s leading AI scientists, Ineffable is developing a new generation of algorithms that learn through experience – more like humans do.

Instead of being trained only on vast amounts of existing data, these systems interact with their environment, test ideas, and improve over time, allowing them to discover new solutions and insights on their own – opening the door to breakthroughs in science, medicine, engineering and beyond.

Sovereign AI and the British Business Bank will co-invest in the AI firm, supporting the company as it builds its technology, grows its team and scales its operations from the UK.

The company is led by David Silver, one of the most influential figures in modern AI.

A Professor at University College London and formerly Head of Reinforcement Learning at Google DeepMind, his work helped power some of the biggest AI breakthroughs of the last decade, including AlphaGo – the system that famously beat the world champion at the game of Go.

He founded Ineffable to take the next leap forward: building AI that can go beyond imitation and generate genuinely new knowledge.

A bet on Britain

Sovereign AI is designed to be different from any previous government-backed unit, acting like a venture capital fund with the muscle of the state behind it, moving fast, backing ambition and cutting through the red tape that so often holds brilliant ideas back.

It will invest directly in the UK’s most promising AI startups, help them scale quickly, and give them the support they need to compete with the best in the world.

“The world needs a place where the full ambition of the reinforcement learning paradigm can flourish,” Silver said.

“A place where the deep question of intelligence is faced head-on: how to discover new knowledge from experience in the environment. I have a unique opportunity to build this place, using my leadership, vision, track record, and the strength of my team.”

Science and Technology Secretary Liz Kendall said that Sovereign AI is a bet on Britain.

“We believe in this nation’s entrepreneurs and innovators, and we are backing them to seize the benefits of AI for the UK.

“This investment in Ineffable will support a company at the very frontier of AI, with the potential to transform entire sectors, underlining our determination to ensure that the UK isn’t just an AI taker but an AI maker.”

The $1.1 billion round eclipses all previous European seed rounds and signals surging investor confidence in UK-based frontier AI research.

Silver has committed to donating 100% of any personal proceeds from his equity in Ineffable Intelligence to charity via Founders Pledge.

Now read: UK property marketplaces are in an AI arms race