Paula Byrne’s gripping new account of Evelyn Waugh’s life, Mad World, has been greeted with enthusiasm. Byrne’s book — like Madresfield: The Real Brideshead, by Jane Mulvagh last year — traces the story of the house that inspired Waugh, and its unhappy inhabitants: Lord Beauchamp, hounded into exile on account of his sexuality, and his son, Hugh, also gay and alcoholic, and model for Sebastian Flyte.

Despite such blighted lives, we insist on seeing the myth of Brideshead as somehow comforting. It’s a multiplied if equivocal nostalgia. We’re longing for a world we never had — a world Waugh was yearning for even as he wrote his book in 1945, in the aftermath of apocalypse and the shadow of austerity. In the same way, as I began to read Waugh and Mitford in the 1970s, my generation laboured under its own mushroom cloud, as well as the imminent collapse of British society.

From Biba to Bryan Ferry, we suckled on a sense of past glamour. And although the anarchy of punk sought to destroy all that, the Thatcher era re-immersed itself in Merchant Ivory and Charles Sturridge’s masterly adaptation of Brideshead. (It is a little-known fact that at the time Sturridge shared a flat with Alan Erasmus, co-founder of Factory Records, home of Joy Division and Happy Mondays).

Of course it was the clothes. There’s a brilliant description in Mad World that sums up the fetishistic male fashion sense of the Twenties, as embodied by Harold Acton and Brian Howard. “They wore suits by Lesley & Roberts, cut in early Victorian style ... silver, mauve and pink trousers ... cashmere turtle-necked sweaters in bright colours, suede shoes, raspberry crêpe-de-Chine shirts, green velvet trousers, and yellow hunting waistcoats. Harold wore a grey bowler, a trailing black coat and his infamous ‘Oxford bags’ (26in wide at the knee and 24in at the ankle).” The Pet Shop Boys are still working their way through the same wardrobe.

For a young, would-be aesthete languishing in a Southampton suburb in the 1970s, this was the stuff from which dreams were woven. I’d arrive at school — where I was taught by monks — in an astrakhan coat, fedora and cane. Such was the spirit of the times that I wasn’t even beaten up.

Indeed, I carved a career out of my obsession. In the early 1980s I began writing profiles of figures such as Nancy Cunard and Cecil Beaton for the style magazine Blitz — and found an image that changed my life. In 1927 Beaton had photographed Stephen Tennant for the aristocrat’s 21st birthday. That portrait inspired my first book, Serious Pleasures — not so much a biography as a manifesto, a paean to a class and an era that may, or may not, have deserved it.

Posed against a silver-foil background, Tennant wears a suit from Anderson & Sheppard, a cloth-of-gold tie with a jewelled pin. Ostensibly, he might be any City broker — an arch reference to a boom time before the fall.

But Tennant’s suit was a subversion, accessorised with rouged lips and gold dust in his hair. This decadent aristocrat was not so much effeminate as an alien in Mayfair. He transcended gender in the same way that David Bowie, Boy George and Leigh Bowery did in my time, using their sexuality as a kind of armour.

Tennant stares out defiantly, a perfect construction of the era. (Well, almost perfect. It was only last week, when BBC Four persuaded me in front of the camera for a new film, Glamour’s Golden Age, that I noticed Tennant’s comb was visible on the shelf behind him.) That stare spoke eloquently of an unbridgeable chasm — not only in time and style, but in class. Had I been Tennant’s coeval, I would never have been invited to the party. The hermetic seal of privilege — literally, private law — would have excluded me.

Sixty years later I inveigled my way into my idol’s presence at Wilsford, his Wiltshire home. The house had lain undisturbed since before the war. The same straw hats worn by guests at fancy-dress parties in the 1920s still hung on the stairposts. Letters from Virginia Woolf and E. M. Forster littered the carpet, along with paintings by Rex Whistler.

It was my Brideshead moment — an afternoon that caused my heart to ache, as if I too had lived in Arcadia. Tennant — a survivor where his fellow Bright Young Things had fallen away — instructed me in a quivering voice to take the Beaton photograph closer to the light, the better to admire his long-departed beauty. Then I was dismissed from his presence and went back to my box bedroom in Southampton, and began to write.

Glamour’s Golden Age is on BBC Four this autumn. Philip Hoare’s Leviathan won the Samuel Johnson prize

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