Celebrity doctor Christian Jessen is in the "last chance saloon" in his bid to defend a libel action over false rumours Northern Ireland First Minister Arlene Foster was having an extra-marital affair, a Belfast High Court Judge has warned.

Mrs Foster is suing the TV medic, best known for presenting Channel 4 shows Embarrassing Bodies and Supersize v Superskinny, for a tweet Dr Jessen posted on 23 December 2019 making completely unfounded allegations of infidelity.

Even though the Democratic Unionist Party leader has already secured judgment in her favour, Dr Jessen claims he never received legal papers sent to his London address and was unaware the case had reached hearing.

Under cross-examination last week, he told the court that he shut out all news over the last year and moved back to his parents' home because of the pandemic and his deteriorating mental health.

At a review hearing today Mr Justice McAlinden confirmed he will make a preliminary ruling on whether Dr Jessen is telling the truth about the service of documents.

"This is an important aspect of the case, this is the last chance saloon for Dr Jessen," he said.

"If it's a case where he loses his opportunity to belatedly defend this action on the credibility point, then I think it's important that all opportunities are given to him and his representatives to make points in his favour.

"That's the reason why I'm adopting this particular approach."

With both sides confirming they do not intend to call any further evidence, the judge listed a hearing next month for submissions on the reliability of Dr Jessen's account.