IT IS so easy to be wise after the event. The Leeds Hospital inquiry into the Jimmy Savile scandal has had the pundits searching for scapegoats and lamenting the failure of the authorities to listen to warning signs. Too often we assume that an individual's serious misconduct should be obvious, and that, if we have the right procedures in place, abuse can be prevented.

But this is not always true. Liberal societies seriously underestimate the power of individuals to do evil, partly because they can't take the concept seriously. "Evil" is something from a horror movie, entertainly gruesome.

Hannah Arendt came closer to reality when she spoke of the "banality" of evil. She was writing about the trial of Adolf Eichmann. Her point was that most of those who carried out atrocities under the Nazis were perfectly ordinary people who simply did what they were asked to do.

Many of those who, unwittingly, helped Savile to abuse his victims were also perfectly ordinary people: porters, security guards, receptionists. To them, he was a celebrity. They were flattered by the attention he paid them. They turned the keys, opened the doors, wheeled the trolleys, delivered the victims, and failed to notice that anything was amiss.

The same was true of the important people whom Savile courted: the consultants, the managers, the police, the politicians. They liked being associated with the "saintly" and tireless fund-raiser for good causes.

We now know that Savile had no moral compass, and that his eccentric benevolence masked a sense of absolute sexual entitlement. We do not see evil because we do not expect it, and in many ways that is a good thing. But it leaves us helpless when the real thing emerges.

I met Savile in the early 1970s. He had his own much-admired Speakeasy programme on Radio 1, produced by the BBC's Religious Department. As a new researcher, I can remember him coming through the second-floor corridor at Broadcasting House in his clownish outfits, hair streaking behind him, a gag a minute.

Was there something sinister about him? There were rumours. All I felt at the time was that he was odd, but I didn't have much experience of celebrities.

I think his producer, Roy Trevivian, knew that there was a serious problem. His preparation for Savile's arrival was a couple of triple vodkas laced with lime. We all had too much invested in Savile's success. And that is how he made fools of all of us. Evil knows its targets.

The Revd Angela Tilby is Diocesan Canon of Christ Church, Oxford.