Lady Longford, popular and respected historian, Labour supporter for 70 years, and one of the last of the bright young things of the 1920s, died yesterday aged 96.

Her daughter, Lady Antonia Fraser, said her end came "peacefully in her sleep, like a Sleeping Beauty" at her home in Hurst Green, East Sussex.

She leaves 22 books, eight children, 26 grandchildren, and seven great-grandchildren in a talented family of more than 60 people.

Her husband, the penal reform and morality campaigner Lord Longford - of whom his wife said: "Frank never stops talking" - died last year aged 95. They had been married for 70 years.

Lady Antonia said her mother had recently been in a nursing home but had decided to return to the family home. "She was not suffering from any particular illness, she simply died of old age," she said. "She was a well respected lady and tremendous person."

One of Lady Longford's last appearances was on Radio 4's Desert Island Discs earlier this year. The record she most wanted to take with her was I Vow To Thee, My Country. For books, she chose two historical works, Diplomacy and Murder in Tehran and Imperial Russia's Mission to the Shah of Persia.

Lady Longford, daughter of two London doctors related to the Chamberlain political family, only began her literary output in 1954, aged 48, when she had finished having children.

Her first big success was the prizewinning Victoria RI in 1964, followed by a biography of Wellington. Among her other subjects were Byron and the royal family.

As one of the few women of her time to go to Oxford, she was considered the chief beauty of her undergraduate generation. She was in the social set which included Evelyn Waugh, John Betjeman and the future don Maurice Bowra.

But she also taught for the Workers' Educational Association, an experience which made her a socialist.