TV presenter Dr Christian Jessen “constructed a reality which did not exist” during a series of podcasts he produced during lockdown, the High Court in Belfast has heard.

Northern Ireland’s First Minister, Arlene Foster is suing the celebrity medic for defamation over a tweet he posted making an unfounded claim that she was having an extra-marital affair.

On December 23 2019, he published the tweet to his 300,000-plus followers. The tweet remained online until Dr Jessen deleted it on January 7 2020.

A key issue in the case is the TV doctor’s repeated failure to engage in the legal process and respond to papers served on him by Mrs Foster’s representatives.

The doctor, best known for appearing in the Channel 4 show Embarrassing Bodies, first engaged with the legal proceedings after Mrs Foster had already given evidence to the court.

He claimed he had been previously unaware the case at Belfast High Court was happening.

He previously told the court that he had moved out of his London city centre flat at the time and into his parents’ home as he was suffering from mental health issues and had not been watching the news.

In the High Court in Belfast on Friday, judge Mr Justice McAlinden questioned the TV presenter about a tweet he had sent on January 26 this year about graffiti near Waterloo train station.

The judge said: “That gives the impression that you are in that area regularly, you see that it is not there one day, it is there the next day  – so that gives the impression that that is where you live.”

Dr Jessen said: “I certainly didn’t want it made public at the time that I was living with my parents and that I wasn’t particularly well.”

The judge asked Dr Jessen about a letter that he had sent, with a number of other doctors, to ensure a social media platform removed a video produced by David Icke during the Covid-19 pandemic.

David Icke is a conspiracy theorist who had his Twitter account suspended last year for communicating Covid misinformation.

“That would appear to give the impression that you are reaching out and seeing what is happening in the world around you, seeing what is happening in relation to issues which are of interest to you, and in a condition which enables you to participate in a joint effort.”

Dr Jessen said: “This is a really good example of the way in which us minor celebrities blow our own trumpet.

“All that was involved was that (TV’s Countdown presenter) Rachel Riley had contacted me and said she was leading this campaign to do this, would I put my name to this letter, it was as simple as that.”

The judge then asked Dr Jessen about a series of podcasts he had made during lockdown.

Mr Justice McAlinden referred to a podcast in which Dr Jessen had referenced taking part in video games on his X-Box with his partner.

He said: “That is an impression of a domestic scene with your partner in an apartment of some nature. That is a world away from someone who is living an isolated life with his parents.”

Dr Jessen said: “One of the many pernicious aspects of depression is the way one can hide it. It is the way one can disguise one’s feelings and can carry on with life.”

Another podcast referred to Dr Jessen and his partner engaging in a video chat with friends to cheer them up during lockdown.

He told the court: “You create a persona, it is not necessarily actuality. I am very conscious that plonkers like me can give advice that is a million miles away from our own lives.”

The judge said: “In essence what you are saying is that these events didn’t happen. You were constructing a reality which didn’t exist to provide a good example for others.”

Giving evidence last month, Mrs Foster said she felt “humiliated” after the celebrity doctor tweeted the unsubstantiated rumour of an extra-marital affair.

Later, the judge heard submissions from counsel for both sides on Dr Jessen’s claim that he did not receive legal papers from Mrs Foster’s lawyers.

Dr Jessen’s council Gavin Millar QC said there was no record of his client being dishonest and described his podcasts as a “piece of entertainment”.

He said: “He podcasts as a doctor, it is partly for entertainment, it is partly to maintain his profile. It is a piece of entertainment, they have artistic licence, it is not vaguely comparable to lying on oath.”

Mrs Foster’s counsel David Ringland QC said of Dr Jessen: “He compounded his problems today in the witness box when he was trying to explain away the inexplicable in relation to tweets and podcasts.

“The idea that someone like him, an entertainer no less, is entitled to be dishonest because that is apparently an entertainer’s licence and for a good reason, that is a different type of dishonesty, that is stretching credibility to breaking point.

“The detail he has gone into would conform exactly with what he says he was doing. This idea of a construct doesn’t stand any form of examination.”

The judge adjourned the case to consider the submissions.