As the god of wine, lover of peace, and inspirer of ecstasy, it is easy to see why Dionysus was one of the more popular figures in the Greek pantheon. The cult that grew around him eventually spawned the theatre, too. But although, according to mythology, those who performed the sacred rites for this jovial son of Zeus were principally women, female actors were banished from the Greek stage.
This decision of the ancients was to have surprising and enduring ramifications over the following millennia. It meant that for centuries, men would have to play women and Dionysus unwittingly became the god of the modern-day drag queen, the patron saint of the stuffed bra, the lord of the false eyelash and the glamour wig.
It was a tradition that guided the careers of performers through the Shakespearean age to the Victorian music hall. Today, it defines stars from the pop charts to the Big Brother house. In the guise of Paul O'Grady, aka Lily Savage, it has just conquered the chat-show sofa.
Cross-dressing among the olive groves, while setting the trend in Western theatre, was not unique, however. Dr Aoife Monks of Birkbeck College, London University, who has studied the phenomenon, says the tradition manifested itself across the world independently of the Greeks.
"The exact origins have become largely lost in the mists of time," she says. "But we do know that cross-dressing is central to early performance and it is one of the few universal theatrical forms. It was and always has been the norm, and not abnormal, to cross-dress."
By Shakespeare's time women were still banned from the stage by law. The Tudor age regarded the very suggestion of women taking to the stage as harmful and damaging to audiences - which ironically included many women who dressed as men to escape public censure for daring to venture out without a chaperone.
The ever-inventive Shakespeare enjoyed the ironies thrown up by the social conventions of the day. In Twelfth Night the beautiful young Viola changes name and gender and breaks the heart of the Countess Olivia while dressed as the handsome Cesario. According to Dr Monks, Shakespeare's "wink" to the audience requires complicity and acceptance of the joke - a man playing a women, playing a man, who in turn fools a man playing a woman. It is only because everyone knows that Cesario is really a woman that the play gives so much pleasure.
And this conceit lies at the heart of the theatrical cross-dressing phenomenon, she explains. "The theatre operates as a space for creating new social forms and desires. It is somewhere new identities can be imagined and inverted. But it is not about passing off a man as a woman or making them seem real. The pleasure is in knowing that the actor is cross-dressing - enjoying the contradictions between the reality and the actor. We have to know the difference. If we didn't know, we wouldn't enjoy what was happening," she says.
The ban on women appearing on stage was not to last. The Puritans' influence waned during the Restoration period, but there were also creeping concerns that audiences might be turned on by the sight of handsome young men dressed as pretty young women.
Restoration theatre, while bad news for the ranks of male actors who specialised in female roles, provided a huge theatrical opportunity for women, but it was still considered a scandalous career and the roles of actress and prostitute blurred.
Women appearing in opera invoked the ire of the pontiff himself. Pope Clement XI was moved to remark: "A beautiful woman who sings on stage and keeps her chastity is like a man who leaps into the Tiber and keeps his feet dry." The Catholic Church, of course, would have nothing to do with women - neither in its clergy or its choirs. Castrati - young boys castrated before they reached puberty - helped papal choirs hit the high notes until the dawn of the last century.
But it was the English Victorian theatre that was to witness the greatest number and widest variety of cross-dressing roles and Dr Monks traces a direct link between straitlaced societies and on-stage gender switching.
"When you have a rigid notion of how men and women should act, in the theatre you get this space where fantasies and what some may describe as perversions, can come to life," she says. But the fantasy was a cruel one and built on fear and insecurity, she claims.
Nowhere was this more apparent than in the increasingly popular character of the pantomime dame. Other scholars have debated why women should be portrayed in such an unappealing fashion - old, sexually predatory and physically grotesque - and why they delighted the working-class audiences that flocked to see them.
Laurence Senelick, professor of drama at Tufts University and author of The Changing Room: Sex, Drag and Theatre, explains: "The menopausal woman was considered dangerous if she was sexual. Treating her comically and having her played by a man has the effect of neutralizing her," he says. Modern-day depictions of the pantomime dame, though still essentially grotesque, have been substantially sanitised. The tradition of principal boy, this time a man played by a woman who courts the leading lady, adds an erotic same-sex thrill while removing any genuine romantic appeal, it is argued.
While 20th-century theatre has experimented with cross-dressing roles in an attempt to challenge audiences in avant garde or feminist productions, the fashion for theatrical realism and naturalism has seen the number of roles fall. Serious productions of Shakespeare have returned with men in female roles, notably those by Mark Rylance at the Globe Theatre, but all in the name of historical authenticity. Women by contrast continue to find it difficult to be taken seriously playing men - witness Fiona Shaw's controversial Richard II at the National Theatre in 1995.
Television, by contrast, has ruthlessly exploited the public's appetite for watching men parading as women across their screens. As late as the 1980s, up to 20 million viewers would tune in to watch the two Ronnies, Corbett and Barker, perform the much-loved finale to their weekly sketch show. Harnessing the finest traditions of music hall, the two comics would sport drag for the closing song and dance number. The reason, says Dr Monks, is historical. "TV, particularly British television, has its roots in the theatre. There is a carry-over of traditions, actors and audiences, all of whom take pleasure in similar techniques," she explains.
Danny la Rue was one of the first to take cross dressing to the wider British public. He first donned drag during a naval concert party in Singapore, eventually becoming one of the highest paid entertainers of the Sixties. Bob Hope even described him as "the most glamorous woman in the world".
He was also the first female impersonator to appear at the Royal Variety Performance before the Queen, but in an even more daring move, Stanley Baxter was the first female impersonator to do an impression of the Queen (earning him the wrath of clean-up TV campaigner Mary Whitehouse).
During the Sixties and Seventies, few comedians appeared able to resist the allure of dressing up. Even Monty Python - regarded as subversive and mould breaking by their legions of fans - was an all-boys club, with Cleese, Chapman et al keeping all the funny female parts for themselves.
For more traditional comics, like Les Dawson, drag was an unlikely but highly popular extension of his Northern working-class humour. Likewise The Dick Emery Show which ran for 20 years. It is best remembered for Mandy, the confused blonde, who saw double entendres at every turn - a menace she saw off with a swing of the handbag and the immortal line: "Oooh, you are awful ... but I like you."
Others such as Kenny Everett sought to bring a more cutting edge to female impersonation. His most celebrated female character - a pneumatic-breasted, strangely bearded American B-movie actress - was originally to be called Mary Hinge. Consternation among BBC executives saw him modify it - but not much - to Cupid Stunt.
The advent of more politically aware alternative comedy in the late Seventies saw cross-dressing once again fall out of fashion. When Freddie Mercury strode into the video of Queen's I Want To Break Free dressed like a female character from Coronation Street, it had an adverse effect on the band's career in the United States for nearly a decade.
Other pop stars were more lucky, if less overt. Mick Jagger appeared on stage in what resembled a white dress as early as 1969, but waited nearly three decades before going the whole hog in the 1997 film Bent.
Jagger's once-rumoured bed partner David Bowie made a career out of flirting with androgyny. But "gender-bending" was to come of age only in the Eighties, and the queen of the New Romantic movement was Boy George. Real name George O'Dowd, he enjoyed major international success with Culture Club for four years, spawning an army of imitators - among them Pete Burns, the cross dresser whose outsize pout is currently gracing our television screens from the Big Brother House.
Film, too, has moved a long way from the traditional cross-dressing format of a man forced to dress as a women to avoid recognition, a plot device which achieved its apotheosis at the hands of Tony Curtis and Jack Lemmon in Some Like It Hot. Both Dustin Hoffman and Robin Williams scored success with drag roles in the comedies Tootsie and Mrs Doubtfire and humour has become the natural redoubt of the modern-day drag queen. David Walliam's unconvincing transvestite in Little Britain and her insistence that "I am a laydee, you know" has become a ubiquitous catchphrase.
The distinction between transvestite and theatrical cross-dresser is an important one, however. Essentially a 20th-century medical definition, many transvestites say their choice of dress is designed to please them alone. Grayson Perry, the cross-dressing potter and Turner Prize winner, says: "The perfect transvestite experience would be traipsing along the street with someone holding a gigantic mirror in front of me so that I could see myself the whole time. As I can't, wearing crippling shoes or being a tad cold reminds me I'm in the wrong clothes."
On the stage, screen or television, it is about pleasing the audience. And it's been doing that for more than 2,000 years.