But the film critic David McGillivray, speaking immediately after a group of nudists were seen bouncing around shaved of all innuendo, suggested that evangelising the cause of naturism was never a primary motive among film-makers. Actually what he said was, "Let's not beat about the bush, these were intended as sex films."
Thus did one titteringly placed double entendre set the tone: while the concluding part of Empire of the Censors (BBC2), which immediately preceded it, took a serious, analytical, certainty-disturbing approach to the social implications of film classification, Doing Rude Things might have been sub-titled Carry On Censoring. Indeed, taking its lead directly from the films it was to investigate, the programme revealed that characteristic British response: if in doubt, snigger. And nothing makes us more doubtful than sex.
So here was Angus Deayton - TV's Mr Sex, remember - dressed in the kind of dinner jacket favoured by cinema doormen in the Fifties, running the full range of documentary delivery styles from arch to arch, as he wondered why it was that as the core got harder in Europe, in Britain we found it easier to titter over the tits.
The easiest - and probably most accurate - thing to do in these circumstances is to do what the programme did: blame the Establishment. Reared in public schools, its attitude to sex films back then was, as it was on most things, somewhat hypocritical.
Hence the nice scene in which Deayton, watching some daft piece of naturism in a mock-up of a sleazy cinema club, has his view of the fundaments obscured by the hat of the bishop sitting in front of him. If you thought that was just a piece of silly throwaway, the intervention of the marvellous Pamela Green suggested it was a piece of decidedly accurate satire. Green - the well-endowed star of many an early sex production, who still appears, 30 years on, to have her best work in front of her - remembered the time in 1964 she was up in court on an obscenity rap for some film about as racey as a 1995 shower gel commercial. The judge asked to see the evidence in the privacy of his own chambers. Needing to be certain he was seeing what he thought he was seeing, he did this three times. And then he dismissed the case, saying that he would like to purchase a copy of the film "to take home for my sons". Which is a judicial variation on the old excuse when asking for a celebrity autograph.
In fact, the most revealing thing about the programme was that anecdotes like this were far more chortle-worthy than the film-clips. There was Robin Askwith, star of the dire Confessions cycle, and living proof of the youth-enhancing benefits of romping buttock-deep in a kitchen full of soap-suds, for instance, being so self-deprecatingly droll about the making of his movies, it suggested that the producers would have been far more successful in their aim to amuse if they had forgotten their dreary fantasy and simply recorded the behind-the-scenes reality. Instead they presented a genre of movies that were failures on both counts: neither titillating nor remotely funny. Typically British, then.
Having shown us how it should be done on BBC2 last week, David Letterman has returned to New York. So now the delights of his Tonight Show (Sky One) can be witnessed only by those with the rare combination of a satellite dish and the ability to switch away from the Sports channel.