National treasure, adored by the public, comic genius - it's become almost a cliche now for those qualities to go hand-in-hand with a troubled private life.

This one-off documentary explores the side of Tommy Cooper that audiences never got to see and suggests that in order to achieve all the success, fame and ­popularity that his career gave him, he made a deal with the devil to get it.

Not literally, although you won't find many people here with a good word to say about his life-long manager Miff Ferrie, who died in 1994. "He was the most unpleasant agent I've ever known. Nobody liked him," offers one interviewee in tonight's programme.

As well as having absolutely no sense of humour - a serious drawback when your clients include Tommy Cooper and Sir Bruce Forsyth, who also appears here - one of Ferrie's other eccentricities was to keep obsessively detailed records of every one of his phone ­conversations.

Perhaps he knew what a gift these would one day be to biographers and documentary makers because these never-before-seen documents form the backbone of this film, revealing new details about Cooper's drinking, his ­volatile marriage, and his equally rocky relationship with Ferrie himself.

But if you'd prefer to remember Cooper as the funny man with the fez on his head, there are plenty of classic clips of his stage act here, too.

Gruff-voiced comic and skilfully inept magician Tommy Cooper was adored for his shambling genius. For 30 years this endearing, befezzed buffoon charmed TV viewers with disarming gags ("My teeth itch") and cloddish conjuring.

Crazy-haired, and flat-footed, the 6ft 4in Cooper looked a disaster. Which is why audiences laughed before he'd even uttered a word. I especially loved the way he made his voice crack with exasperation when things went wrong.

In real life, things went very wrong indeed. This painfully honest profile exposes the destructive demons that drove him to drink and violence. But fans including Brucie and Doddy remind us of the magic of the man.

TV review: The Untold Tommy Cooper

You didn't need to be a Tommy Cooper fan to find this take on his life compelling.

Comedian Tommy Cooper was regularly credited with the ability to be funny without actually having to do anything. At 6'4!, with messy hair and a red fez on his head, he certainly looked the part. Using previously unseen footage, plus details from the diaries of Cooper's manager Miff Ferrie, this documentary provides a portrait of the troubled comedy giant, who died in 1984. Contributions come from Johnny Vegas and Damien Hirst.