It is the legal showdown that has pitted two of the biggest names in tech, Elon Musk and Sam Altman, against each other. At stake is the future of one of the world's most valuable start-ups, ChatGPT-maker OpenAI, along with the reputations of Altman - the company's boss - and Musk, the man he founded it with. The central claim the jury has now retired to consider is Musk's argument his former friend "stole a charity", cheating him out of a fortune (albeit a tiny one, by Musk's standards) along