The Hay Festival was told yesterday that when La Bohème blasts out across Trafalgar Square next month, the audience will primarily be the direct descendants of the Bohemian morals embodied in the opera's origins.

Henry Murger's Scènes de la Vie de Bohème first brought blushes to British readers in 1845. But in the 1890s Puccini seized upon its tales of free-loving, carousing students burning furniture to keep warm amid poverty in the cause of art.

Virginia Nicholson, the author of Among the Bohemians, told the 600-strong audience that when the performance takes place on July 7 the London crowds will nearly all be the heirs of Bohemia in their lifestyle, morals and ideas.

"We're all Bohemians now," she said.

Mrs Nicholson is the great-niece of Virginia Woolf, whose Bloomsbury group of artists was only part of a tradition of Bohemian "experiments in living" which flourished in Britain from 1900-1950. Some of their lives ended in suicide, fatal illness, alcoholism, drug addiction or the despair of late middle age, fates that befell artists including Woolf herself, Katherine Mansfield, who caught gonorrhoea and died of tuberculosis, the poets Roy Campbell and Dylan Thomas, and the painter Augustus John.

Others - including Arthur Ransome, who later became Guardian Moscow correspondent and wrote the Swallows and Amazons books, and Kathleen Hale, creator of the Orlando the Marmalade Cat children's books - were so poor in the pursuit of their art that they went without food.

Mrs Nicholson said: "We have to recognise that many of our present assumptions about life have originated from people who, sometimes in very small ways but motivated by revolutionary ideals, hope and defiance of convention, challenged the establishment 100 years ago.

"In a way, we're all Bohemians now. We can conduct relationships with people from any social class without fear of ostracism, while deploring oppressive, stratified societies.

"Our choice of friendships and love affairs is our own. The idea of chaperonage makes us laugh; women are independent. We recognise that children have potential which must not be squashed.

"We take it for granted that society is fluid, that informality will prevail. We do not expect to behave like marionettes at any social gathering. We are hatless, relaxed and on first name terms with people we barely know.

"We live in a society that most people's grandparents would hardly recognise.

"After four years of researching their lives, I am full of admiration for the heroic, starry-eyed quality which these Bohemian idealists brought to the simplest details of their lives.

"And I am sure it was that intensity - the friendship, fun, colour, above all the freedom of that life - which despite all the hardship made it worthwhile."

CK Stead, who was there to discuss his novel about Katherine Mansfield, added a caveat about Bloomsbury Bohemianism: "They had the insecurity of the rich who are poor, not of the poor who are poor."

Mrs Nicholson said Bohemi ans had "a very strong psychic distaste for money, for lucre". When they had it, they spent or gave it away.

In Among the Bohemians Mrs Nicholson writes that today's life has lost some good qualities, partly through the influence of Bohemianism, "Graciousness and sobriety perhaps, and the measured graduation from formality to intimacy in human relationships. Sex often precedes friendship rather than the other way round.

"Self control is often an inadequate substitute for rules. New social neuroses have replaced the old."