Joan Wyndham, who died April 8 at 85, came from an eccentric upper-class family and as a young woman led a disreputable life which she unflinchingly chronicled in four volumes of memoirs. An aspiring actress, heroic drinker, jitterbug dancer, and Benzedrine-fueled bohemian, she enjoyed an outrageous reputation, and held court in “Swinging London,” with an entourage of dissipated followers.

To social historians she was golddust, being one of the few women happy to go on the record — and on camera — to discuss sex in general and her virginity in particular, which she shed early in the war after renting an artist’s studio in Redcliffe Road, Chelsea. “One night there was a really bad raid and the whole shelter was shaking, and I thought: ‘Ah well!'” she explained on British television recently.

In the 1970s Wyndham became the restaurant critic for the French guide GaultMillau, jetting between London and New York; later she was a cook at the Royal Court Theatre. Defying social conventions all her life, she once unexpectedly defied medical convention too: after years of suffering from painful gallstones, and submitting to the divided opinions of expensive doctors, she found herself cured in an instant when she was hit by a truck.

Only in her 60s did Wyndham turn her wartime diaries into memoirs. These chronicled the adventures of a young woman on the loose in wartime London, living it up with the likes of Quentin Crisp (“hair down to his shoulders”), Philip Toynbee (“sick on the sofa”), and Dylan Thomas.

When she was 21 she had an affair with the “so unbearably attractive” 17th Lord Lovat, a Scottish war hero. In describing their assignation over partridge at the Ritz, she not only kissed, but told all, unsparingly, in another memoir, “Love Is Blue” (1986).

In July 1943, in a taxi in Soho, Dylan Thomas, who had pinched her bottom in a pub, “smothered me in wet beery kisses.”

After the war, she decided against attending Oxford. “Five years of regimentation,” she explained, “have left me with a lust for liberty that has to be satisfied.” Later she came to regret that decision.

Joan Olivia Wyndham was born on October 11, 1921 at Clouds, the Victorian sandstone house in Wiltshire built by her great-grandfather, the dandy Percy Wyndham. She spent her first three years there, hazily remembering that it had 40 bedrooms and a kitchen so far from the dining room that food was transported on a miniature railway track. Her father, Richard, known as “Dirty Dick,” had inherited Clouds during the First World War.

Wyndham’s parents divorced when she was 2, and she was sent from the age of 7 to boarding schools. At 15, she fell in love with the young John Gielgud; having seen him as Hamlet, she “sometimes followed him home so that I could kiss his doorknob.” She later transferred her affections to “the totally gorgeous” Laurence Olivier and the dancer Robert Helpmann (“gosh, what a bottom!”).

In 1937 Wyndham went to the Royal Academy of Dramatic Art, but left after a year. Nearly 70 years later she published a witty account of her time at RADA in her memoir “Dawn Chorus” (2004). Her wartime diaries, “Love Lessons” (1985) and “Love Is Blue” (1986), described her service with Britain’s Women’s Auxiliary Air Force.

She spent her first week’s leave with a bearded Czech artist who picked her up and took her home to his rented room in a former brothel, lived in by Dylan Thomas and owned by a woman with the telegraphic address Chastity, London.

During another drunken fling in London en route to a new posting in Inverness, Wyndham woke up fully clothed to find a man, naked beneath a black mackintosh, standing

at the foot of her bed. Their subsequent amorous encounter did not please Wyndham’s new paramour, a Hungarian called Zoltan, whom she abandoned on learning that he had a wife. At Inverness she fell for a handsome Norwegian naval first lieutenant, marooned in port during repairs, who cut notches on her bedpost with an enormous commando knife, and from whom she caught fleas.

Despite being appraised as “a very peculiar type of officer, not amenable to discipline, and a bad example to other ranks,” Wyndham was promoted to flight officer. At one point she was taken up for a spin by the youngest squadron leader in the Polish Air Force, and recorded that it was “the first time I’ve ever had my bottom pinched at 3,000 feet.”

After the war she met and married her first husband, Maurice Rowdon, a scholar whom she followed with her newborn daughter, Clare, to Baghdad, where he had landed a teaching job.

Meanwhile, Wyndham’s father had been shot dead by a sniper while covering the Arab-Israeli war for the Sunday Times, and she used her inheritance to buy a small cottage. She was startled to learn that Dick Wyndham had been “one of Europe’s great flagellists,” and had been known as “Whips” Wyndham.

Wyndham’s affair with her Russian lodger produced another daughter, Camilla. After spells as a horoscope writer, working in a theater, and as a publisher’s reader, Wyndham moved to Oxford to open the city’s first espresso coffee bar, complete with jukebox. She divorced and remarried, to the Russian lodger, and worked for a time at Housewife magazine before becoming a prominent figure on the art scene in the mid-1960s.

In later life she came to dislike cooking, but nursed passions for whiskey, cigarettes, the television program “Blind Date,” and Diana, Princess of Wales. An operation to remove a tumor in 1989 robbed her of her sense of taste, and although her memory faltered in old age, she managed to produce a further two volumes of memoirs: “Anything Once” (1992) and “Dawn Chorus” (2004).

Joan Wyndham is survived by both her husbands and by both her daughters.