Lawyers for Vernon Unsworth, the British cave diver hitting Elon Musk with a defamation lawsuit after Musk called him a "pedo guy," unveiled new documents in the lawsuit on Monday.

The documents contain an email from Musk to a public-relations agent in which he called himself a "f---ing idiot" for telling a BuzzFeed journalist in an email that Unsworth was a "child rapist."

Unsworth's lawyers allege Musk paid a private investigator not only to dig up dirt on Unsworth but also to feed information to the British press.

The documents reveal how Musk came to deeply regret his extraordinary allegations against the cave diver.

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Elon Musk privately called himself a "f---ing idiot" for calling a cave diver a "child rapist" in an email to a journalist.

Court documents made public Monday night in a legal battle between the cave diver Vernon Unsworth and the Tesla CEO have shed more light on the fallout from Musk's evidence-free allegation on Twitter that Unsworth was a "pedo guy."

Musk first called Unsworth the name in a tweet sent in July last year. The professional diver had criticized Musk's proposal to rescue a Thai soccer team trapped in a flooded cave in Thailand using a submarine — a move Unsworth described as a publicity stunt.

The following month, after receiving an email from the BuzzFeed News reporter Ryan Mac, the 48-year-old tech executive emailed the journalist with a barrage of fresh allegations, claiming without offering evidence that Unsworth was a "child rapist" who married a 12-year-old and urging Mac to investigate. Mac subsequently published the email, which Musk had prefaced with "off the record." (Mac had not agreed to an off-the-record exchange in advance.)

Read more: Elon Musk hired a PI to dig up dirt on cave diver Vernon Unsworth. That guy is reportedly a felon.

The new court documents from Unsworth's lawyers include emails Musk sent to a public-relations agent after the debacle, indicating how he came to regret his extraordinary allegations against the cave diver. "I didn't expect Buzzfeed to publish an off the record email," Musk wrote. "My intent was to have them investigate and come to their own conclusions, not publish my email directly. Still, I'm a f---ing idiot."

"In the past, Buzzfeed has respected emails prefaced with 'off the record,' but this time they did not," he added. "It was still one of the dumbest things I've ever done."

The 12 boys and their coach were rescued from a flooded cave system in July last year. REUTERS/Soe Zeya Tun

Unsworth's lawyers allege that Musk and Mac's interaction was not the only example of the CEO trying to feed stories to the press about Unsworth.

James Howard-Higgins, a private eye hired by Musk to dig into Unsworth, was also tasked with feeding information surreptitiously back to the press, the new documents indicate. An email to Howard-Higgins from Jared Birchall, the head of Musk's family office, said: "We would like you to immediately move forward with 'leaking' this information to the UK press. Obviously must be done very carefully."

A previous set of documents in the case first revealed that Musk had hired Howard-Higgins to defend himself, and BuzzFeed subsequently reported last week that Howard-Higgins had a history of fraud. In a deposition, Musk said he came to believe that the reports being sent back to Musk's family office were "just taking us for a ride."

Unsworth's UK lawyer Mark Stephens alleged to Business Insider that Musk's email to BuzzFeed News and Howard-Higgins' instructions to leak to the press showed a common attempt to manipulate the media without explicitly naming Musk as the source of the information. "It's exactly the same strategy," he said.

Unsworth's lawyers also claim that Howard-Higgins never gave Musk any information about Unsworth marrying a 12-year-old. "Nothing in [Howard-Higgins'] report would reflect or give grounds to say that," Stephens said.

Musk's lawyer Alex Spiro told Business Insider in a statement: "This case is nothing but a money-grab in which Unsworth has pursued profit and self-promotion at every turn."

Here's the full legal filing: