Elon Musk dropped a “nuclear bomb” on the life of a British cave expert he called “pedo guy” in a Twitter spat, a court has heard.

Vernon Unsworth is suing the Tesla co-founder for defamation, over a tweet sent following the 2018 Thai cave rescue.

 Musk, said to be worth more than 20 billion US dollars (£15 billion), denies “pedo guy” was an allegation of paedophilia and instead argues it was a mindless insult.

A trial is under way in a California federal court.

On Friday, Lin Wood, Unsworth’s lawyer, delivered his closing argument and told the jury the impact being called “pedo guy” had on his client.

“He (Elon Musk) dropped a nuclear bomb on Vernon Unsworth,” Wood said, adding its “fallout” would affect him for the rest of his life.

His relationships, his friendships and his jobs would all be coloured by Musk’s tweet, Wood said.

Wood, at times standing within touching distance of Musk, described the billionaire as a “liar” who was attempting to deceive the jury.

Wood also suggested to the jury they should award Unsworth punitive damages of 150 million US dollars (£114 million), assumed damages of 35 million US dollars (£26.6 million) and actual damages of five million US dollars (£3.8 million) should they find Musk guilty of defamation.

He said his offer of a mini-submersible to help with the rescue was a publicity stunt and dismissed Musk’s argument that “pedo guy” was no more than a mindless insult.

Musk’s lawyer is set to deliver his closing arguments to the jury in Los Angeles.