Tens of thousands in the British tech sector gathered at London’s ExCel Centre in April for the opening of Amazon’s AWS Summit, the tech giant’s biggest event outside the US. As delegates took their seats in the vast main hall, AWS’s Europe chief, Tanuja Randery, arrived on stage to begin her introductory remarks.

Or so everyone thought. In fact, as the real Tanuja would shortly confirm, the crowd had been watching an AI-generated video of her, put together with a few simple prompts. Amazon wanted to showcase the best-in-class technology that was being built on its cloud platform. The company chose an avatar made by Synthesia.

Fast-forward nine months and Synthesia has found itself the most valuable generative AI company in Britain, having secured a $2.1bn valuation following its £146m Series D round….