BEWARE your former friends would seem to be the lesson hidden in Call Me Dave, the unauthorised biography of David Cameron, written by Michael Ashcroft and the journalist Isabel Oakeshott.

Along with that famous old saying about never placing a private part of your anatomy in a dead pig’s head.

Of those two sentences, one possibly demands a little more context. Having said that, the common phrase “you don’t want to go there” might also have its uses here too.

Lord Ashcroft was once pally with Cameron; now he is perhaps less so. Once he donated around £8 million to the Conservative Party. His money allowed him to flirt with the inner Tory circle: another place most of us wouldn’t want to go. Any one of Dante’s hellish circles might well be preferable to that.

Ashcroft has admitted he has a grudge against Cameron for passing him over for a significant government job, but apparently denies that he is trying to settle a score. I think that is called trying to throw your custard tart and eat it too.

The dry political part of this scandal concerns exactly when Cameron knew about Ashcroft’s status as a ‘non-dom’ in tax terms. Ashcroft says the prime minister knew about his tax status all along, including presumably when he was handing out fistfuls of dough to the Tories. Cameron maintained around the time of the 2010 election that the matter was between Ashcroft and the taxman.

But enough of that brittle old controversy, what about the dead pig’s head? Ashcroft’s book is being serialised in the Daily Mail – so this is a real bit of Tory infighting. Pedigree dog eating pedigree dog. Or pedigree dogging weeing up against the front door of his old friend’s manor house.

Quite how that newspaper’s readers felt when reading about the pig’s head allegation hardly bears thinking about. Especially if pig was on the breakfast menu.

The book alleges that while at university Cameron was a member of the decadent Piers Gaveston club and he placed “a private part of his anatomy” into a dead pig’s mouth as part of an initiation rite. Unsurprisingly, a prime ministerial press spokesman has denied that Cameron ever belonged to such a club. And wouldn’t you love to have been present when the answer to that press question was put into pained words.

In the book an anonymous MP says he has seen photographic evidence of the incident. This is problematic. If the witness is unnamed, it dents your faith in what is being said. And then there is this: does the photograph even exist?

Photographs did once exist of the young David Cameron dressed up to the snooty nines as a member of the room-trashing Bullingdon Club. All copies of that photograph mysteriously disappeared a long time ago. So just imagine the effort that would be put into destroying all copies of the young Cameron being intimate with a dead pig (allegedly).

Meanwhile, George Osborne is in China where he has just agreed a £45 million deal on pig semen – this is true, by the way.

As you might expect, Twitter has been aflame with pig jokes, pork remarks and bacon puns of the sort I won’t repeat here (well, my mother does read these jottings from the ledge).

Another allegation is that while at university Cameron sat around smoking weed and listening to Supertramp. Now that truly is shocking, but just the sort of thing people get up to at university.

In a sense all of this is a distraction from more important matters about what David Cameron is doing now, rather than what he might or might not have done with a dead pig’s head while at university.

Mind you, all this could give rise to some salty political slogans at the next election. Labour can have this one for free: Vote Tory? I’d rather stick my… well, you can imagine the rest.