Lawyers who represented rugby player Paddy Jackson in the Belfast rape trial have issued defamation proceedings against former Ireland captain Rory Best, it can be revealed.

The lawsuit relates to a radio appearance by the recently retired sports star in January, in which he expressed regret at having attended the high-profile trial.

Other comments he made during the interview prompted legal correspondence from solicitors acting on behalf of the team which represented Mr Jackson during the case.

Court records now show the matter has escalated and a writ of summons has been issued against Mr Best (37), who earned 124 caps for Ireland during a glittering career.

As part of the action, two solicitors and two barristers who acted for Mr Jackson are seeking damages from the former Ulster and Ireland hooker for libel. The case was initiated on March 20 in the Queen’s Bench Division of Northern Ireland’s High Court by solicitors Kevin Winters and Joe McVeigh, both of Belfast firm KRW Law, and barristers Brendan Kelly QC and Stephen Toal BL.

They were all part of the legal team which successfully defended Mr Jackson against charges of raping and assaulting a 19-year-old woman in June 2016.

Mr Jackson’s former Ulster team-mate Stuart Olding was also acquitted of rape following the trial in 2018.

Their friend Blane McIlroy was found not guilty of exposure, while a fourth accused, Rory Harrison, was found not guilty of concealing evidence and attempting to pervert the course of justice.

Mr Best, who lives in Co Armagh, had agreed to appear as a character witness for Mr Jackson and, along with fellow international Iain Henderson, he attended the trial on the first day of the complainant’s evidence. But his presence in court prompted a huge backlash, including an online campaign to have him dropped as Ireland captain.

It also prompted questions for the IRFU and then head coach Joe Schmidt. Ultimately, Mr Best did not give evidence at the trial.

Following his retirement he opened up about the controversy during an interview on Newstalk’s Off The Ball sports programme in January.

He expressed regret for attending the trial, saying: “It turned it into a circus and it put a lot more pressure on something that was very sensitive.”

To date no proceedings have been issued against Newstalk or publications who reproduced extracts from the interview.

In his recently published autobiography, Mr Best said he didn’t hesitate when Mr Jackson phoned him and asked him to be a character witness.

He said he had not thought he would upset anyone by attending court and the scale of the “blowback” afterwards came as “a huge shock” to him.

“I didn’t really understand the complexity of the situation,” he wrote.

Despite their acquittals, both Mr Jackson (28) and Mr Olding (27) had their lucrative contacts with Ulster and the IRFU revoked following an internal review into their conduct.

The review focused on sexually explicit WhatsApp conversations involving the players and their friends about the incidents at the centre of the rape trial.

Belfast Telegraph