Elon Musk formally apologised in court in Los Angeles to Vernon Unsworth but insisted his “pedo guy” tweet had been a joking insult and he had not been accusing him of being a paedophile.
Looking directly at Mr Unsworth, the Tesla boss said: "I apologised in a tweet and again in the deposition, and I'll say it again: I apologise to Mr Unsworth.”
Musk, who grew up in South Africa, insists it was common there to use the term “pedo guy” to refer to a “creepy old man'' and he said he used the term instinctively after Unsworth insulted him.
The court heard Musk had offered to build a mini-submarine to rescue the boys and the row started after the 12 boys had been rescued from the water-filled cave
In a TV interview Mr Unsworth referred to Musk’s offer as a "PR stunt" and suggested the American "stick his submarine where it hurts".
Musk watched the TV clip and reacted angrily with a series of tweets on 15 July 2018, including the notorious “pedo guy” tweet.
Musk told the jury in Los Angeles: “It was wrong and insulting, so I insulted him back. It was an unprovoked attack on what was a good-natured attempt to help the kids.''
He testified: “Just as I didn't literally mean he was a pedophile, I'm sure he didn't literally mean shoving a sub up my ass.”
During opening statements, Musk’s lawyer Alex Spiro referred to the interaction as “joking, taunting tweets in a fight between men.''
But Mr Unsworth’s lawyers say that when Musk was asked on Twitter if he thought Mr Unsworth was a paedophile he replid: “Bet ya a signed dollar it's true.'”
Musk also told a Buzzfeed reporter who asked him about Mr Unsworth’s threats to sue over the tweet: “Stop defending child rapists.”
Mr Unsworth, who was praised by the Thai king and the British prime minister, is seeking unspecified damages for pain, suffering and emotional distress from Musk, whose net worth exceeds $20 billion.