What a vile piece of work Colonel Gaddafi was.

For some of you, perhaps, this will be a statement of the glaringly obvious. But I suspect there will be many others for whom, like me, this week’s Storyville documentary on the barbarity of his regime — Mad Dog: Gaddafi’s Secret World (BBC4, Monday) — was something of a revelation.

Sure, we’d all heard about the funny stuff: the time John Simpson went to see him and he farted noisily (Gaddafi, not Simpson) through the interview; the ridiculous outfits; the bullet-proof Bedouin-style tent that he insisted on bringing on his last world tour, complete with live camels to graze decoratively outside.

But the nastier stuff came as news to me: killing his foreign secretary, then keeping him in a deep-freeze in his palace so that he could regularly have a gloat over the body; visiting classrooms of 15- and 16-year-old girls, patting the ones he fancied on their heads, then having them dragged off by his security, gynaecologically inspected and shown pornographic videos (to educate them in his expectations) before raping them and then having them put away in asylums; deliberately shooting down one of his own domestic airliners, partly for the sheer hell of it, partly as a ruse to show the West that its sanctions were hurting Libya so badly that it couldn’t afford to maintain its own aircraft…

Perhaps I’m being naive here, given the murder outside the Libyan embassy in London of PC Yvonne Fletcher, not to mention the destruction of Pan Am 103 over Lockerbie. A dictator capable of such barbarities, surely, would be capable of anything? Well, yes, indeed. But how could we be sure he was personally responsible? Maybe the former was the work of ‘rogue elements’? Maybe the latter — as has occasionally been suggested — was really the work of Iran?

What becomes pretty clear watching this fascinating, supremely well-researched documentary — filmed everywhere from South Africa to Cuba, interviewing everyone from his arms dealer Frank Terpil to his head of protocol and one of his female bodyguards — is that Gaddafi was in it up to the neck in all these crimes and more. We haven’t even touched, yet, on the victims of every IRA bomb containing Semtex shipped from Libyan ports; nor on the women and children butchered in the Sierra Leonean and Liberian civil wars that Gaddafi bankrolled and that cost the lives of more than a million people.

So why was nothing done about him earlier? Well, partly it’s because he was so paranoid and his security was so tight it would have been impossible to assassinate him. (A plastic surgeon who had come to smooth out his wrinkly features recalled on the programme how he had had to operate on Gaddafi at 2 a.m. in one of his secret bunkers, and using only a local anaesthetic, so great was the dictator’s fear of being killed in his sleep.) And partly it was because he was so extraordinarily weird that it suited everyone’s interests to treat him as a joke.

It suited Gaddafi’s interests, obviously, because it enabled him to get away with murder, while terrifying his people and perpetually wrongfooting his subordinates with his Caligula-like capriciousness. It suited the leaders of the West — Reagan and Thatcher among the few exceptions — because Libya’s oil reserves were too useful.

I’ve long been sceptical of the ‘it’s all about oil’ argument beloved by leftists. But in this case it seems to have been true. One US intelligence agent recalled being asked by the CEO of a big oil company whether her government planned to continue with sanctions. When she said ‘Yes’ the CEO burst into tears.  Some elements in the US government were so eager to resume normal relations with Libya that they even proposed smearing the families of the Lockerbie victims. ‘How about we announce to the media that they got insurance money and show them as money-grubbers?’ one person suggested.

When Gaddafi wasn’t killing or torturing people he was seducing them with his oddball charm and his silly money. Libya’s oil revenues, during his reign, amounted to $1 billion per week, so he could buy almost anyone — from top US special forces veterans to top German rocket scientist Lutz Kayser (who was interviewed for the first time from his private island in the Marshall Islands) — or anything. He came close at one point to buying the entire nuclear arsenal of Kazakhstan — 100 nuclear bombs.

Perhaps this was our biggest problem with Gaddafi: he conformed so closely to our stereotype of a cartoon fantasy villain we couldn’t quite believe he was for real. Or, as that US intelligence agent put it, ‘He was so different we just did not know how to deal with him. He was untouchable.’

Still, he’s dead now. Sodomised multiple times then shot, apparently. You imagine he wouldn’t have wanted it any other way.