The pain of Robbie Coltrane: Split from his wife, ordered to lose 7st and in agony from arthritis, the actor returns to TV after years as a virtual recluse 

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Robbie Coltrane (pictured) had not had a lead role in a television drama for seven years 

Robbie Coltrane was in typically pugnacious form at a screening of his new TV drama earlier this month.

He complained with a grandiose wave: 'These are the smallest biscuits in London. I've blown bigger things out of my nose.'

Coltrane, now 66, held the room in his giant hand; there was hearty laughter at his joke.

His observations about serial rapist Jimmy Savile were likewise accorded respect. 'I always thought he was a creepy wee s***e,' he said.

For some time, Coltrane has dropped out of public view. He has not had a lead role in a TV drama for seven years. Aside from some voice-over work on film animations, he has barely worked since finishing filming Harry Potter And The Deathly Hallows — Part 2 in 2010.

It's been a desperately tough period: his marriage to sculptor Rhona Gemmell has ended and he has been in daily agony with osteoarthritis. He won't talk about the end of his marriage but of his health he said recently: 'I'm in constant pain all day.

'I had an exploratory operation and they discovered I had no cartilage left in one of my knees. It's completely disintegrated.' He is waiting for surgery that will repair his joint by glueing a piece of plastic to the bone after it has been shaved flat.

Doctors told him — when he was thought to have been more than 20st — he must lose 7st or risk facing life as a 'cripple', and he is still attempting to reach the target weight in order to be given treatment. He has 2st to go and walks with a cane.

Home is a beautiful rural barn conversion outside Glasgow. There are barely any neighbours and this private man is able to cherish his peace and quiet. Neighbours at a Glasgow address where his two children and former wife live say they have never seen him there.

Het met teenage student Rhona Gemmell (right) in a pub on Christmas Eve in 1988

His marriage broke down in 2003, with reports of a reconciliation in 2008. Now, though, the split is permanent and he has a girlfriend, about whom he declines to speak.

Aside from the osteoarthritis, there have been other concerns about his health.

In January last year, there was an alarming episode when he was rushed from a plane to hospital.

One fellow passenger on the flight from London to Orlando contended that Coltrane, who has made no secret of his fondness for booze in his youth, appeared to be drunk and was 'wheeled' onto the plane. His agent, however, said he was suffering from the sudden onset of flu-like symptoms and was recovering well in hospital in Florida.

He may, of course, have been wheeled onto the plane because of his stricken knees. For his part, he has said nothing about it — which is so typical of Robbie Coltrane. He detests most of the modern media.

Some salty comments have also been made about autograph hunters. He struggles with 'intrusive' fans who have 'no respect' for him.

'When you're out in public, it's fine, but not when you are in your more private moments, like sitting on the beach with your children,' he has said. 'People don't seem to realise this is always like this for me. I know this is the only time they are going to meet me but I have done this 20 times in the last hour.'

No wonder, then, his forthcoming role as a fictional veteran comedian in a major new Channel 4 series is drawing so much attention.

In the four-part drama, inspired by the police investigation into the sexual abuse perpetrated by Jimmy Savile and others, Coltrane's character is accused of historical rape offences. Julie Walters plays his loyal wife. The talk is that this is a performance as good as — maybe better than — his riveting criminal psychologist Fitz in Cracker.

He is seen half-naked, walking with a cane. In one scene, he is shown crying as a woman accuses him in court of raping her decades earlier — and he, in turn, contends that he has no memory of it.

We will have to wait for the TV drama to see whether Coltrane's character is found guilty, but it's clear the subject matter has affected him profoundly. His tears on screen, he said in an interview, were real: 'I didn't have to act at all. The evidence was so heartbreaking. I mean, if you're not moved by that, you might as well hand in your human-being cards.'

Given the sensitivities involved in a TV drama about sex abuse, he knows there may be a backlash. This very intelligent, privately educated son of a forensic surgeon and pianist insists that he is braced for criticism.

'I don't care,' he told the Guardian. 'I think it's important to do this on behalf of the women who were raped, on behalf of all the people who were abused.

'Drama has always illuminated what's actually going on in society, in a way that the news or the internet doesn't . . . the writing is absolutely beautiful. There's total respect for people who actually were attacked.

'That's the important thing for me. If you were raped, what is your life like thereafter, and what would it be like to stand up in court and talk about it?'

We may not be accustomed to Coltrane playing a monster, but he has long been adept at conjuring an edge of menace.

Interviewers routinely come away slightly intimidated by him. He will say 'don't write this down or I will kill you' and will deride any questions he feels are beneath him.

Doctors told him — when he was thought to have been more than 20st — he must lose 7st or risk facing life as a 'cripple'

Born Anthony McMillan, he has never been the sort to suffer fools. He attended Glenalmond College, one of Scotland's top public schools, and 'didn't accept the hierarchy'.

School rules were treated with scorn, and he has boasted of physical fights, saying that because he was a 'big strong boy' he 'didn't take any s*** from anybody'.

The shortage of girls was also a problem for the teenager: 'By the end of term, you used to find yourself fancying the cleaners, who were all about 48, with moustaches.'

He went to art school in Glasgow, where he dropped his posh accent, watched pretentious foreign movies, grew his hair long and experimented with drugs.

Then he moved into a squat in London and tried acting, becoming a leading light in alternative comedy, with roles in The Comic Strip Presents, The Young Ones and Blackadder.

At around this time, he was well-known for 'rampages' around Soho — boozy, promiscuous behaviour. One party trick was biting chunks out of a wineglass and chewing it around his mouth.

In Coltrane's words, his younger self was 'a bottle-of-whisky-a-day-or-nothing man.' He once admitted: 'I can drink a gallon of beer and not feel the least bit drunk.'

His then girlfriend, artist Robin Paine, complained that he was horribly unfaithful. That all changed when he met teenage student Rhona Gemmell in a pub on Christmas Eve in 1988. They went on to have a son, now 24, and a daughter, 19, and moved to the countryside.

There, he enjoyed his hobby of buying and restoring vintage cars, and enjoyed family life. As he put it: 'You are brought up to believe that if you are smart enough and read enough books you will find the meaning in things.

'But all the things that happen to you in life that make you happy or excited or fulfilled have nothing to do with finding the meaning in things at all; having children, for example, falling in love.'

Of course, the end of the marriage was a serious blow. He reportedly checked into the Priory clinic in Glasgow in 2003 and was said to be at 'rock bottom' and in 'a bit of a state'. Rhona began a romance with a TV executive.

In an interview in 2004 Coltrane said that he had suffered from a 'mid-life crisis' upon realising that he was no longer 'a bit of a dude'.

'It's the fear that you're past your best,' he explained. 'It's the fear that the stuff you've done in the past is your best work. It's like when someone dies and they say: 'He'll always be remembered for that show he did in 1972.' But he'd been working for 30 years after that.'

In taking on possibly the most ambitious role of his career with National Treasure, it rather sounds as if there is little danger of that.

• National Treasure is on C4 at 9pm on Tuesday.