Teresa Cuthbertson, the last of the Bright Young Things

Photographed by Cecil Beaton, adored by Evelyn Waugh, at the centre of London's social life in the 1920s, she spent the last six decades of her live quietly with her sister.

Eighty years after their highjinks and high spirits diverted London in the 1920s, the very last of the original Bright Young Things, Teresa Cuthbertson, has died, a month short of her 103rd birthday. Teresa, always known - much to her annoyance - as Baby, was an early, ardent, but unrequited love of the novelist Evelyn Waugh. He captured the spirit and eccentricity of Teresa's scene in his second celebrated novel Vile Bodies (1930) and drew on a number of their circle for his cast. He had already drawn some of them into his first novel, Decline and Fall. Observers have identified aspects of Teresa in Julia Flyte, the leading female character in his opus, Brideshead Revisited.

Teresa was born in 1907, the younger daughter of Nico Jungman, a Dutch-born artist who settled in Britain, and his wife Beatrice, the daughter of a staunchly Roman Catholic Birmingham family. After their divorce in 1918, Beatrice became the second wife of Richard Guinness. She was an innovative London hostess, mixing the aristocracy and the upper classes with artists and celebrities at her house in Great Cumberland Place.

Nevertheless, Teresa and her sister Zita were brought up as strict Catholics and it became a firm foundation throughout their long lives. After school, Zita joined her mother's social world and, with Teresa, attracted her own set. She and Baby were guests at the grandest houses. They were photographed by Cecil Beaton and painted by the society portraitist, Ambrose McEvoy. She had many rich and titled suitors; but, like Nina Blount in Vile Bodies, she fought them off.

Filling in time between parties, the sisters and their best friend, Lady Eleanor Smith, daughter of Lord Birkenhead, devised intricate practical jokes. Baby would dress up as a young Russian émigré widow, Madame Anna Vorolsky, with her "leetle boy" to educate and priceless jewels for sale. She attended a garden party as Mme Vorolsky, leading two borzois, and on being introduced to a distinguished old soldier and his wife, she told him she would never forget the night they spent together in Paris during the war. The general replied coldly that he had only spent one night in Paris during the war. "Zat," said Baby, "was zee night." After this episode, Madame was never seen again.

The trio also conceived the treasure hunt, an elaborate game which involved tearing about London in search of items that were all but impossible to obtain, such as the spectacles of the Archbishop of Canterbury. Between the parties and pranks, the sisters would attend church and do community work. A richer, rowdier set soon took up these capers. Where Teresa and Zita had used buses and the Underground for their treasure hunts, their successors took to the streets in Bentleys and Rolls-Royces. The girls bowed out.

In June 1940, to the chagrin of her many old suitors, Teresa married Graham Cuthbertson, a Scot serving with a Canadian regiment. This recalls shades of Julia Flyte's unsuitable husband, Rex Mottram, in Brideshead, although many suspect Churchill's friend Brendan Bracken was Waugh's model. By 1945 and two children, the marriage was over. Cuthbertson remarried soon after but, in keeping with her Catholic beliefs, Teresa never did.

Zita too had wed briefly and divorced and, at the end of the war, the sisters went to live together. The rest of their lives was to be as rural and calm as their youth had been urban and zany. In 1953, Waugh visited them in their cottage in Gloucestershire and was reassured to find that tales of their poverty were exaggerated. But, more than 20 years later, the diarist James Lees-Milne came to see them and described them as hard-up. Yet nothing could persuade Teresa to sell or show anyone her huge cache of letters from Evelyn Waugh, despite their value. Lees-Milne reported that young people would come just to sit at their feet, and listen to their voices.

In 1990 the sisters, having sold their house, applied for rooms in a convent, and were presented with a questionnaire. The first question was: "Are you incontinent?" They had no idea what this meant, but imagined it must be a good thing and answered: "Yes, very." Both, Lees-Milne reported, were refused admission. In 1995, they moved again, into a beautiful garden cottage built on the grounds of Leixlip Castle, the Irish estate of Teresa's son-in-law, Desmond Guinness. It was there that Teresa died peacefully on June 11 four weeks short of her 103rd birthday.

Teresa was born in July 1907. Her only son, Richard Cuthbertson, was killed in a car accident in 1964, aged 22. Zita died in February 2006, aged 102. They had lived together for close to a century. Teresa is survived by her daughter, Penny Guinness. * The National