Elon Musk has escalated his feud with the British caver involved in July’s rescue of a group of young Thai footballers, whom he had previously accused of being a paedophile.

Vernon Unsworth, 63, angered the technology billionaire when he derided his offer of sending a mini submarine to assist the rescue, pointing out that it was not a workable solution.

Mr Musk responded with a baseless attack in a now-deleted tweet, calling Mr Unsworth a “paedo guy”. He then issued an apology, and said he had tweeted “in anger”.

Last week he reignited the controversy by mocking Mr Unsworth for not following up on his threat to take legal action.

It later emerged that Mr Unsworth’s lawyers had in fact sent Mr Musk a letter on August 6, informing him of their intention to sue for the “false and defamatory statements.”