Philip Hensher: You and your friends can come out of the closet now, Mr Humphries

In the 1970s, the likes of John Inman had to deny their homosexuality in spite of their obviously gay acts. But why are modern gay comics still peddling the tired old stereotypes?

One of the oddities of postwar English life was the degree to which the explicitly homosexual was both forbidden and condoned. Until 1967, homosexual acts were illegal, and, long after that, many homosexuals hesitated to be open about their sexuality. And yet, on the radio and on the television, before and after the 1967 Act, homosexuality was as open as it could conceivably be. In the licensed comedy of Frankie Howerd, Kenneth Williams, John Inman, Larry Grayson and half a dozen others, the figure of the homosexual was packaged up and delivered with a snigger into the nation's living rooms. What could not be acknowledged in real life could be positively welcomed in the form of a Saturday night mass-media saturnalia.

This curious phenomenon has resurfaced with a re-examination of Frankie Howerd's reputation. A television film starring David Walliams focused on his terror of his sexuality, and of its becoming public. Walliams, of course, though not identified as gay himself, is one part of the duo behind Little Britain. That programme achieved enormous popularity with a revival of the gay stereotype. There are other frankly gay comedians and presenters at work today – Alan Carr, Julian Clary, Graham Norton. What has changed between the 1970s vein of lurid innuendo and the 2008 version?

It goes back much further than the 1970s. Before the First World War, blatantly homosexual acts could be found at the music hall; the best known of them remains Fred Barnes. He shot to fame with his innuendo-filled song "The Black Sheep of the Family"; in later years, he was banned from the Royal Tournament as being "a menace to His Majesty's Fighting Forces". Years after his death, homosexuals were said to start a pick-up with, "Do you know Fred Barnes?"

The golden age of the camp comedian, though, must be the 1960s and 1970s. It is a matter of constant bafflement that Kenneth Horne's radio series, Round the Horne, could attract such large and appreciative audiences for a pair of homosexuals, Julian and Sandy, who talked mostly in the gay slang, Polari. Kenneth Williams, who died 20 years ago this Tuesday, was in reality a highly intelligent and cultured man, as his diaries and letters show. The curse of the camp comedian was, however, that he could not be allowed to venture beyond the role that had been assigned him by his sexuality, his voice, and his face.

For some people, that role was clearly pretty well enough. Charles Hawtrey, Williams's co-star in any number of atrocious Carry On films, went on playing the same mincingly flirtatious and yet sexless figure on screen for years. In real life, he descended into an alcoholic haze, living in eccentric squalor in Deal, Kent, and trying to pick up any old passing trade – he was banned from most of Deal's pubs by the end of his life.

Comedy rests on the inversion of firm reality. Comedy in the 1970s was peculiarly reliant on the ancient amusement of men dressing up as women, and the tactic wasn't limited to comedians whose shtick was camp, or who in real life were homosexual. Stanley Baxter, Les Dawson, or the five-times married Dick Emery made a career out of dressing up as women for everyone's amusement. There were very few possibilities for a real woman in comedy, Marti Caine and Faith Brown being more or less the extent of it.

Sexual inversion was already a key feature of English comedy. If clearly heterosexual entertainers could amuse audiences by dressing up as women, then the gay entertainer could, surely, find a place. The place, however, was achieved at the cost of deniability. Frankie Howerd could never have contemplated being open about what, from his stage act, might have seemed perfectly obvious. The interesting case here is the late John Inman. Not only did Inman go to extreme lengths to conceal his own sexual preferences, almost to the brink of his civil partnership with his long-time boyfriend, he also, ludicrously, denied that his most famous part, Mr Humphries in Are You Being Served? was intended to be homosexual at all. "He's just a bloke who lives with his mother," was the much-repeated formula.

The lurid flamboyance of Grayson, Inman, Julian and Sandy, and Hawtrey made perfect sense at the time. It matched with perfect neatness both the forbidden nature of homosexual display, and the inverting formulae of comedy. What is really difficult to understand is quite why exactly the same thing should still be continuing today. It's not a question of propriety or political correctness; just of the obvious fact that some things generally stop being funny over time. Why, given the increasing openness and visibility of gay men in the past decades, does the old-fashioned style of gay innuendo still exist?

Homosexuality, in fact, is still shocking and unacceptable to the mass media. It retains its force as an anarchic agent of comedy because it hasn't become familiar or understandable. Clary, Norton, and Paul O'Grady were cheerily lurid at the start of their careers, but in styles quite distinct from the old-fashioned innuendo. Clary really was talking about buggery in a manner which barely stretched as far as the double entendre.

And yet, as they progressed towards a mainstream audience, their material was winnowed out by the cultural commissars. Norton on a Saturday night is a pale shadow of his former self; deprived of filth, he basically has no resources to fall back upon. Alan Carr, currently shrieking his way through the same tired old material on Channel 4, will surely follow the same route.

Gay comedians of the new school have often expressed their enjoyment and even admiration of the old-fashioned school, seeing in Howerd and Inman not a tragic statement of the closet militant, but men who, in this one setting, were able to revel in their sexuality. Russell T Davies, the creator of Queer as Folk and current Doctor Who writer, has spoken of his bafflement at what he sees as a politically correct and humourless response to Mr Humphries and the like.

Many gay comedians since the 1990s have revived the manners and style of the old gay comedy, removing the element of deniability. Nobody is going to debate whether Carr or Clary are gay in the way that – it seems incredible now – people used to debate whether Kenneth Williams was.

There seems to me an element of nostalgia in the current rash of camp gay comedians. I doubt that it will continue indefinitely. The truth is that, 30 years ago, a visibly gay man could be presented to a wider audience only through comedy and its inversions of social order. Larry Grayson, and his talk of his friend Everard Farquharson, was allowed on the television because it was, could only be, funny.

Nowadays, things have changed rather. We have, for instance, Evan Davis, presenter of the Today programme and much-admired bringer of complicated economics to the masses. He is somebody who it is difficult to imagine existing 30 years ago; someone clearly an urban gay man in his style and manner without being the slightest bit camp, who is not there to be funny or to make innuendoes. Sooner or later, despite the blandishments of the heterosexual majority who want to be entertained by people they actually despise, most gay men will see that as being rather more worth aiming at than being wheeled on once in a while to talk smut.

One of the saddest revelations of a life of Frankie Howerd is that his shtick – the "Ooh, missus!" outrage and the verbal mincery – wasn't his normal way of speaking at all. He couldn't do it spontaneously. He could only perform from a script, written for him by other people. There is something emblematic about that; the truth is that the gay performer always inhabits the role assigned to him, by others. That situation, surely, is now nearly at an end.