What's The Matter With Tony Slattery is a sensitive portrait of comic’s struggles after blinking out of the public eye

You don’t actually have to know anything about TV comedian Tony Slattery to find this hour-long BBC Horizon special immensely moving.

It is the story of a lifelong struggle with depression, misdiagnosis and drink dependency, but it is also more than the sum of its parts. It is, at times, both funny and hopeful. There are very few of us who won’t be touched by it.

For the uninitiated, such as myself, who only dimly remember Tony (I think we should, in the spirit of intimacy, use first names rather than the more unforgiving “Slattery”) twinkling on Dave reruns of Whose Line Is It Anyway?, a recap.

Tony was — and is still — a hugely likeable and talented Cambridge Footlights alumnus, from the class of Messrs Stephen Fry (who makes an important intervention in Tony’s journey here), Emma Thompson and Hugh Laurie. He was a mainstay of British TV’s bygone silly circuit until 1996 when, amid rumours of a breakdown, the gifted comic blinked out of the public eye.

At the time, bipolar disorder was discussed but never confirmed. “It’s a truly democratic disease — it can hit anyone,” he observes. Now, aged 60, he wants his mental health reassessed.

Granting astonishingly gracious access to his own struggles — sudden swings from bubbly openness to shuttered darkness, a destructive cocaine habit that at one point saw him consume 10g a day, and an inability to see himself ever being free of drinking — Tony provides us with a tough watch.

He talks openly, but stutteringly, of the paranoia that afflicted and consumed him, culminating in an episode in which he threw every electrical device from his riverside apartment into the Thames. He is also, still, immensely amusing, a wonderful entertainer. “That’s a very serious face, Tony,” his interviewer puts to him, as one chuckle fades suddenly. “I can’t help it,” he says, his smile crumpling. “I’m a very serious person.”

In a moment that should, in this day and age, perhaps come with a trigger warning, he later recalls — for the first time, and perhaps inadvisedly on camera — a horrific episode of child abuse. You’d throw your telly out the window too.

The object here is not to ghoulishly pick over tabloid morsels, though. It is to point out paths to recovery. One in four people will be affected by mental illness during their lifetime, we are informed. The past has to confront the present, Tony himself is told.

This is an immensely sensitive depiction of that journey, from our first reintroduction to Tony and his immensely supportive partner of more than 30 years, Mark Hutchinson (and Molly, their “psychotic cat”, who also seems very sweet).

Their love for each other is incredibly strong, but “it’s tiring”, as Mark admits, “having to care for someone who is constantly on the edge.” Poor Tony, who constantly berates himself for “self-indulgence”. Poor Mark, watching the man he cares for self-consume. Tony is, as the excellent Oxford professor Guy Goodwin tells him, lucky still to have the love of so many when so many others do not.

It is mental health awareness week. Be kind, is all I’ll add.

Horizon: What's The Matter With Tony Slattery airs tonight on BBC Two at 9pm