Singapore Airlines, whose new Airbus A380 contains private suites with double beds, recently warned its passengers not to join the mile high club, as the suites aren’t soundproof. In English law, cases have periodically arisen from the unusual locations in which sex has been practised — including on planes.

In March 2000, a charge of "outraging public decency" followed an incident in which Mrs Amanda Holt was alleged to have performed oral sex on Mr David Machin, whom she’d just met, during the middle of a transatlantic flight. Passengers were upset by the loud moaning and squealing noises, while one passenger was kicked in the head when the liaison reached a pitch of excitement.

The charge, however, was eventually dropped and they were convicted of being drunk on a plane contrary to Air Navigation Order 2000, SI 2000/1562, art 65(1), and fined a total of £2,500.

The offence of “outraging public decency” arose from the historic role of the courts as protectors of public morality. For a conviction, it must be proved that something was of a "lewd, obscene or disgusting nature". Since 1663, this has included a variety of sexual conduct outside the bedroom, including a schoolmaster "behaving in an indecent manner with a desk" in front of two boys.

In 2006, Keith Rose was convicted of outraging public decency after he was caught on CCTV at night having oral sex with his girlfriend in the foyer of a Lloyds TSB bank in Sheffield. There were no witnesses but the branch manager saw the film the next day. Quashing the conviction on appeal, however, Mr Justice Burnton said it wasn’t enough that someone saw the event on film afterwards. There had been “no act which actually outraged public decency since there had been no public to outrage”.

Other cases have hinged whether sexual activity could physically have been performed in particular locations.

In one case in 1836, it was necessary to judge whether it was physically possible for Tommy Taylor, a wealthy lawyer, and a Mrs Mellin to have had intercourse on the 1ft 10in shelf of a wooden stile in a field near Wakefield. It was ruled that, on balance (so to speak) intercourse could have occurred on it.

And in a case in 1945, an adultery allegation turned on whether couple with a “long history of passionate intimacy” could have copulated “in a semi-recumbent position” on the front seat of a lorry parked outside Stockton-on-Tees. Mr Justice Wallington took the view, evidently relying on his own knowledge of the interior of lorry cabins, that intercourse wouldn’t have been possible.

But the Court of Appeal disagreed. The couple, it ruled, already knew their way round a sexual encounter so well, “there was no element of unfamiliarity or reluctance to contend with”. Just the handbrake and steering wheel. A seasoned divorce lawyer once noted that in his professional experience, sex was possible anywhere except on the ceiling.

The barrister Clifford Mortimer (father of Sir John Mortimer, QC) reported a surprise triumph in a divorce case: “Remarkable win today, old boy. Only evidence of adultery we had was a pair of footprints upside down on the dashboard of an Austin Seven parked in Hampstead Garden Suburb.”

In 1994, the actress Gillian Taylforth sued The Sun for libel. The newspaper had claimed she performed oral sex on her fiancé in a car parked on a sliproad to the A1 near London. When a police officer appeared at the car window, Ms Taylforth had said she was merely providing her fiancé with “abdominal relief” for an acute attack of pancreatitis.

During the libel trial, the entire court moved out to the car park to watch reconstructions of the alleged sexual act in the front of a Range Rover — first with, then without, a seat belt being worn. In testimony, Miss Taylforth presented herself as a sexually reserved character. But during the trial a film was sent to the newspaper’s advocate showing her at a party simulating masturbation with a wine bottle and using a sausage as a prop while boasting “I give very good head.” The film was shown as evidence midway through the trial, and Ms Taylforth lost her case.

Overall, the law’s stance on sex is much the same as that of the Edwardian actress Mrs Patrick Campbell, who said that “it doesn’t matter what you do in the bedroom as long as you don’t do it in the street and frighten the horses”.

Professor Gary Slapper is Director of the Centre for Law at The Open University

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