British prime minister David Cameron has committed no crime

It should be said at the outset: there is no proof that David Cameron performed the act of which he has been accused by a resentful former friend.

What can be said is that, even if Lord Ashcroft's second- hand account is accurate, Cameron has committed no crime, the pig being dead and oral sex not being included in the relevant legislation.

People who stood around watching would, however, be guilty of a criminal offence, as would anyone who viewed any of the pictures of the event that are said to exist. In other words, it can be a criminal offence to view the performance of an act that is not itself a criminal offence.

‘Extreme pornography’

The anomaly arises from the Criminal Justice and Immigration Act of 2009, on to which the Gordon Brown government allowed attachment of a new offence of possessing “extreme pornography”, defined to include necrophilia and bestiality. (Viewing images of a person apparently taking pleasure from a dead pig might be said to breach both provisions, of course, although this proposition seems never to have been tested in court.)

It is widely recognised that British Tories enjoy more adventurous sex lives than members of any other party. In 2014, flamboyant MP and Conservative deputy chairman Michael Fabricant was sacked after tweeting a reference to a llama called Darren, which had been gifted to him by a political journalist.

Fabricant recounted: "When the Sochi [Winter Olympic] Games started, I did a few tweets pointing out that Russia had a very crude and outdated attitude to gays. And someone tweeted at me, 'Are you gay or just pretending to be gay?' I tweeted back, 'What I can reveal is that I am having an affair with a llama, but I won't say if it's a boy llama or a girl llama.'"

Fabricant says now that party bosses ought to have realised this was a joke. Then again, it is the British Conservative Party we are dealing with here.

Avoiding publicity

The 2009 Act hasn’t lain inert on the statute book: cases are running at about 30 a year. Most result in convictions. It seems some defendants plead guilty in hopes of avoiding publicity.

This is not always wise. In December 2009, a judge ordered the release of a man charged with possessing an image of another man engaged in a sexual act with a tiger after it emerged that the tiger was stuffed.

Bestiality has always presented British law with problems. Take the 19th century case of a Warwickshire youth called Hone, sentenced by a judge to 15 years for an “unnatural act” with a hen. His lawyers subsequently discovered that, a few years earlier, the court of appeal had overturned the conviction of a man called Dodd who had allegedly done a duck, on the ground that a duck was not an animal “within the meaning of the Act” of parliament.

Feathers ruffled, the judge wrote to the home secretary, who in turn consulted the attorney general, asking whether the ruling in Dodd and the duck provided a precedent for Hone and the hen. The AG submitted a report to Disraeli’s cabinet pointing out that the appellate court’s decision in Dodd and the duck had itself been based on Collins and the turkey, but that the Collins decision had been overtaken anyway by the case of Brown. (It is unclear with what fowl deed Brown had been charged.)

Physically impossible

The attorney general also made the point that the ruling in Dodd had been based not only on precedent but on the fact that the alleged act was physically impossible, there apparently being things you can do with a hen that can’t be done with a duck.

All this takes us some distance away from Cameron and the pig. But then, this is the nature of the beast. We will cite the case of Gilbert and the cow, which, many readers will agree, gives good example of how these matters might more sensitively be handled. The following exchange makes the point:

Prosecutor: “On the day in question, were you proceeding along a lane adjacent to the farm of Mr Clarke?”

Witness Albert Harris: "I was."

Prosecutor: “Would you describe for his Lordship what you saw?”

Harris: "Well, George Gilbert was standing in the doorway of a barn with a sheep."

Prosecutor: “Yes, and what was he doing?”

Harris: “He was messing with the sheep.”

Prosecutor: “Are we to understand that the defendant was having sexual intercourse with the sheep?”

Harris: “Er, yes.”

Prosecutor: “And what did you do when you observed this shocking spectacle?”

Harris: “I said, ‘Mornin’ George.’”

Now, isn’t there a lesson there for us all?