When David Baddiel agreed to investigate the history and modern face of Holocaust denial for the BBC, the comedian and writer knew there would be a terrible dilemma he would ultimately have to confront.

“If you’re going to talk about the devil, at some point you’ve got to meet the devil,” he says. “I came to the uncomfortable, unhappy conclusion that I was going to have to meet a Holocaust denier to understand the phenomenon.”

An edited version of the encounter between Baddiel and Dermot Mulqueen, an Irishman who spews falsehoods about the Holocaust to 7,000 followers on Facebook, is included in Confronting Holocaust Denial, shown after the BBC’s season marking Holocaust Memorial Day and the 75th anniversary of the liberation of Auschwitz-Birkenau.

Baddiel conflicted

Baddiel remains conflicted over the validity of giving any kind of platform to Mulqueen, who was sent to jail for an act of public vandalism in Ennis, County Clare, committed in protest at Holocaust Memorial Day.

The project is, of course, deeply personal for a high-profile Jewish personality whose latest live show Trolls turns the anti-Semitic abuse he receives on Twitter into satire.

“This goes to a very deep part of me. My mother was born in Nazi Germany, my grandparents just got out. I’m only here by the skin of my teeth.”

“As I grow older, the reality of that and the closeness of it historically becomes clearer to me in a way that it wasn’t when I was young.”

He was motivated by incredulity that the historical fact that 6 million Jews died in the Holocaust, “what I grew up with as certainty and something we always have to remember”, is now “placed on shifting sands.”

Five per cent of UK adults do not believe the Holocaust took place and one in 12 believes its scale has been exaggerated, a recent survey found. A record number of antisemitic incidents was recorded last year with parts of Hampstead and Belsize Park, including a synagogue, were daubed with racist graffiti.

‘Archetypal lie’

Social media has allowed Holocaust denial to spread unchecked. “We’re living in a period of history where untruths have a lot of power. Holocaust denial is the archetypal lie in our culture. My personal feeling is we have to take the trolls on. There is a direct association with real world violence.”

Baddiel’s journey through the mire of denial led him to Facebook’s London HQ.

Mark Zuckerberg refuses to ban Holocaust denial from the platform because he doesn’t want to censor “things that different people get wrong.”

For Baddiel, who debates the issue with Facebook’s head of “policy solutions” Richard Allan, there is no difference between Holocaust denial and hate speech, which is barred.

No benign form of denial

“People who simply misunderstand the Holocaust do not have Facebook sites saying it didn’t happen. Denial is a direct way of saying Jews are liars, they have tricked the world for their own gain. In all my experience, I’ve never come across a benign form of Holocaust denial.”

There’s little benign about Mulqueen, who uses the meeting to expound false theories about the gas chambers, accuses Baddiel of controlling the BBC and, at one point, picks up a guitar to sing a bizarre antisemitic song.

“I’m not Louis Theroux – he’s brilliant and very good with people who have unpleasant views, smiling and drawing them out,” recalls Baddiel, who struggled with shaking his tormentor’s hand.

“To some extent, I just wanted to punch this bloke in the face. That’s not going to draw him out, is it?”

Although he feels “rage, anger and a little bit out of control” when he is confronted with a denier, Baddiel’s trademark wit proves a lethal weapon in exposing the fraud.

Holocaust can be subject of jokes

“There is no subject you can’t make a joke about but you have to be able to justify the joke,” he believes. “I spend a lot of time making comedy out of Twitter abuse. For me it’s a form of healing, turning abuse into feed lines.

By the end of their three-hour exchange, Baddiel almost “felt sorry” for Mulqueen, who discloses that denying the Holocaust gives him a “peace of mind” he cannot find elsewhere in his life.

The confrontation is validated editorially by the inclusion of a quite different encounter, when Baddiel visits Rachel Levy, an 89 year-old who survived the horrors of Auschwitz and Bergen-Belsen, where most of her family were murdered by the Nazis.

“There’s a human awful truth in her story that moves you, that lets you know it is true and therefore to say that this did not happen is obscene,” concludes Baddiel, who believes that the controversial Holocaust Memorial planned for Westminster, which has yet to receive planning approval, must go ahead.

“Preserving the truth is more important than ever,” he says. “It is unbelievable – but true – that humans did this. The truth will always be attacked so that’s why we need to build memorials to it, to say this really happened. Therefore for the people worried about whether or not it will obscure certain views, shut up.”

:: Confronting Holocaust Denial is on BBC2, Monday Feb 17th, 9pm.