A British cave diver branded “sue” and “pedo guy” by tech billionaire Elon Musk was left feeling “humiliated, ashamed and dirtied”, a court has heard.

Vernon Unsworth’s voice cracked as he gave evidence in his defamation case against the Space X mastermind .

The row started when Mr Unsworth, who helped in the underwater rescue of children trapped in Thai cave, dismissed Mr Musk’s offer of aid as a publicity stunt.

Mr Unsworth, who divides his time between London and Thailand, gave evidence at a Los Angeles court on Wednesday and appeared on the verge of tears while describing the impact of Mr Musk's tweets.

Asked how he felt after seeing what Mr Musk's tweeted, he replied: "It feels very raw. I feel humiliated. Ashamed. Dirtied.

"From day one I was given a life sentence without parole. And at times I feel very vulnerable, it hurts to even talk about it."

Mr Unsworth said he felt 'dirtied' by the tweet

Mr Unsworth, a veteran cave explorer who said he first travelled to Thailand in 2011, added Mr Musk's tweet was "very hurtful".

"I find it disgusting," he said. "I find it very hard to even read the word, never mind talk about."

Mr Unsworth was then asked about a follow-up tweet from Musk, in which he said words to the effect of "Don't you think it's strange he hasn't sued me?"

Mr Unsworth said he was "obviously" aware of the post, and asked what it meant, replied: "If I did not (sue) it must be true. Which it is not."

The British diver said his name is "tagged with being a paedophile".

Elon Musk's tweet was widely shared on social media

Discussing the impact of the tweets, he said: "I have probably lost a bit of self-confidence. I have good days and bad days."

"I still feel dirtied," he added.

Mr Unsworth, a financial consultant, told the court he first travelled to Thailand in 2011 with his girlfriend Woranan Ratrawiphukkun, known as Tik.

Courtroom sketch shows Elon Musk during the trial in a defamation case filed by British cave diver Vernon Unsworth

The 64-year-old said he had explored caves around the world and was an expert in the layout of the system the children were trapped in.

He first realised there was an issue when Tik was told by her father on June 24.

Mr Unsworth became heavily involved in the rescue, the court heard.

He met with senior Thai politicians, including the interior minister and sports minister.

During the three days, the 12 boys and their football coach were rescued from the cave over July 8-10, Mr Unsworth said he did not sleep "at all".

Courtroom sketch shows British cave diver Vernon Unsworth during the trial in a defamation case

During the first day of the trial on Tuesday, Mr Musk appeared in court to deny "pedo guy" was an allegation of paedophilia.

The billionaire dismissed it as a Twitter insult between two men having a row.

Mr Musk insisted the phrase "pedo guy" was commonly used in his native South Africa and meant "creepy old guy" and not that Mr Unsworth was a paedophile.

Asked by Lin Wood, one of Mr Unsworth's lawyers, why he did not offer the defence earlier, Mr Musk replied: "I think it would have been worse."

He said "it's like if I called someone a mothereffer," adding it would seem "sarcastic" to say "I did not mean they committed incest".

The trial continues.