Williams was born in
Petersfield,
Hampshire, by ten minutes the younger of identical twins. She and her sister
Barbara Árnason were talented artists, and for six years from the age of ten wrote and illustrated books for each other's birthdays and at Christmas. Both were enthusiastic
Girl Guides, attending some of the movement's first camps, and some of Ursula's early books were collections of stories she had told to her own Brownie pack. The girls were also keen riders – on hobby horses at first. To save for a pony they kept goats, selling their milk which they refused to drink themselves. Thanks to their uncle, the publisher
Stanley Unwin, the twins visited the Alps, which later inspired some of Ursula's most vivid writing, most notably the trilogy that began with
The Three Toymakers. Its final volume, ''The Toymaker's Daughter'', was among her most celebrated creations. Williams's greatest source of ideas, however, was the house in which she spent her teenage years,
North Stoneham House, a large, dilapidated mansion set in woodland north of Southampton. Events from her childhood recur repeatedly in her fiction, with North Stoneham described at greatest length in the 1941
A Castle for John-Peter and depicted in Faith Jaques' illustrations for ''Grandpapa's Folly and the Woodworm-Bookworm'' of 1974. She was a friend of
Puffin Books editor
Kaye Webb, and organised riotous parties for the Puffin Club, of which she was made the first honorary member. She worked with illustrators like
Shirley Hughes, Faith Jaques and
Edward Ardizzone. Much of her later writing included disruptive, but essentially good-hearted children, and was influenced by her work as a juvenile magistrate and as a highly involved school governor. Locally, she was greatly admired for her many acts of kindness and an instinctive
Christian faith. Personal problems, including her brother's threatened suicide, family crises, the death of her husband, the loss of an eye, and her near death to cancer, interrupted her work, but Williams went on writing until the age of 80, and achieved the longest published career of any children's writer of her generation. She married Conrad Southey "Peter" John in 1935. They lived at Hampton, near
Kingston upon Thames, then
Esher, before moving to
Gloucestershire in 1942, and Beckford,
Worcestershire, in 1945. Peter died in 1971. They had four sons, three of whom survived her. She died in 2006 at
Tewkesbury in
Gloucestershire. Many of Williams's manuscripts and further correspondence are held at
Seven Stories, the Centre for Children's Books in Newcastle. An exhibition, marking the centenary of her birth, opened in Winchester in April 2011. ==Books==