Lord Longford thought that his epitaph should be "the outcast's outcast". And by the end of his long and controversial life, he had certainly attained that goal. For, try as he might, the crusading, yet unworldly, politician just couldn't keep out of the headlines. In 1971, the eccentric former cabinet minister published a report on the pornography industry. Having toured many of the country's seedier sex clubs for the purposes of research, he was given the derisive tabloid sobriquet of "Lord Porn".
But Longford invited even greater red-top contempt when for the next three decades - until his death in 2001 at the age of 95 - he waged a campaign for the parole of the notorious Moors Murderer Myra Hindley. His crusade led the tabloids to dub him "Lord Wrongford". But he would not be swayed by public opprobrium. A committed Catholic, he believed passionately in the power of forgiveness; he thought no one was beyond redemption.
Longford, a compelling one-off Channel 4 drama penned by Peter Morgan, the writer of The Queen, Frost/Nixon and The Deal, zeroes in on the liberal peer's vociferous support for Hindley (played by Samantha Morton). Did he sell his good name in pursuit of a lost cause? Was he taken in by a manipulative and heartless killer?
In a beautifully nuanced performance, Jim Broadbent brings a rare humanity to the title role. Even though you often despair of Longford's gullibility, you never once doubt his good intentions. In the very first scene of the drama, he is seen blinking back the tears as he is attacked on a radio phone-in for his naivety in backing the infamous killer. "I want to know how your esteemed guest can look himself in the mirror every morning," rages one caller. "How could you rub salt into the wounds of the family like that? A man in your position, fraternising and campaigning on behalf of that monster."
It is a chilly winter's morning, and I am standing watching the filming of Longford. We are on College Green, the rectangle of lawn outside the Houses of Parliament. Broadbent, in his guise as Frank Pakenham, Seventh Earl of Longford, is explaining to a reporter why he is campaigning for Hindley. As he puts it: "No human being is beyond forgiveness. Condemn people from our armchairs and what have we become?" The director Tom Hooper shouts, "Cut. Very good, Jim," and a runner rushes forward to throw a puffa jacket around the shoulders of the lead actor who, now the cameras have stopped rolling, is visibly shivering.
Back at the unit base in a nearby car park, the actor invites me into his caravan for lunch. Sporting Longford's bald pate, aquiline prosthetic nose and standard-issue "ageing aristo" ensemble of battle-scarred green cardie and frayed checked shirt, Broadbent in person is as gentle and warm as his screen alter ego. He starts by emphasising that the drama - which also features Lindsay Duncan as Elizabeth, Frank's loyal wife, and Andy Serkis as a disturbingly charismatic Ian Brady - is aiming to help rescue Longford's reputation, which has become as battered as his old green cardigan. "The film is an attempt to rehabilitate Longford," observes Broadbent, who won an Oscar for his poignant portrayal of an equally resolute elderly man, John Bayley, in Iris.
"At first, Peter Morgan had this stereotyped image of him in his head. But the more he researched Frank, the more he became a huge admirer of him. At the end of it, Peter thought, 'How we miss this type of politician in this day and age!' Frank was dogged and prepared to be vilified for standing up for what he believed in. He was utterly unafraid to be unpopular.
"Because [Myra Hindley] was a woman, she aroused enormously strong emotions," comments the 57-year-old actor. "The idea of a woman killing children in the way that she did is beyond the pale. So in trying to help her win parole, Frank really was taking on the most difficult area imaginable. Why did he do it? Because he absolutely believed in the possibility of redemption and forgiveness. Having met Hindley, he liked her and thought she was a reformed character."
But wasn't Longford, whom Harold Wilson once said had the judgement of a 12-year-old, naive to believe that she had really undergone such a radical transformation? "I hesitate to say that Frank was naive," Broadbent replies. "I want viewers to make up their own minds. He thought that everyone should be given the chance of being reconciled with the community. He always wanted to see the best in people and found Hindley utterly plausible. He was not alone in that - many other people found her just as plausible."
Like Longford himself, the biopic may raise red-top hackles. That, however, is not a prospect that unduly concerns Broadbent. "There might be controversy from the press, if it means they can get Myra Hindley on their front pages. There's a Longford line - in fact, it was one of the tenets of his life - 'Hate the sin and love the sinner'. My version is that the tabloids flip it round: they love the sin and hate the sinner."
The 33-year-old director Hooper, who recently picked up an Emmy for Elizabeth I, agrees. "If the tabloids do attack us, they'll only be helping to make the point that the film makes about how the media fuels public opinion and tries to interfere with the judiciary. But people now trust the judiciary more than politicians. We don't think politicians can make objective judgements anymore. If the invasion of Iraq had gone through a legal process, for instance, we'd have had a very different result."
Broadbent goes on to underline how courageous Longford was. The actor lists some of the many unfashionable causes that the peer promoted. "In 1942, he helped put together the pioneering Beveridge Report, which paved the way for the welfare state. And after the war, he was a prime mover in the campaign to forgive the Germans and put them back on their feet - another line that did not win him many friends. On prison reform, he was also way ahead of his time. His vision was on a par with Scandinavia, where they have always been more liberal about these things. He'd go to different jails three times a week and was still visiting in his nineties. He didn't drive, so he was hacking by public transport to places as far apart as Durham, the Isle of Wight and Dartmoor."
Hooper thinks the drama has many contemporary echoes. "The central theme is, 'is any human being beyond forgiveness? Can someone's crimes be so bad that it is impossible to rehabilitate him or her into society?' Longford highlights the balance between retributive and restorative justice. That theme now has tremendous, broader resonance about the politics of forgiveness. Look at the way that the US and the UK are executing foreign policy. Their stance is not forgiveness but preemptive retaliation. It's an aggressive approach where you neutralise potential problems in advance. But the question remains: what happens in the aftermath?"
Broadbent is being called away to make-up. It requires four hours each morning to make the actor resemble Longford as an aged man, but he isn't moaning. "Why should I complain? I've found Frank a truly inspiring character. If people take one thing from this drama, I hope they hark back to a better era when politicians still had some idealism. A friend of Frank's once asked him, 'Does it trouble you that you'll be remembered principally as the friend of Myra Hindley?' Frank replied: 'The friend of the friendless? No, that'll do me.'"
Longford is on Channel 4 on Thursday at 9pm