Mary Soames, left, with her parents, Winston and Clementine Churchill, in London in April 1963. Lady Soames wrote several books about her family, including a biography of her mother. (Leonard Brown/AP)

Mary Soames, the last surviving child of British World War II leader Winston Churchill, died May 31 at her home in London. She was 91.

Her son Nicholas Soames, a Conservative member of the British Parliament, confirmed the death but did not specify a cause.

Born Sept. 15, 1922, Mary Soames was the youngest of five children of Churchill and his wife, Clementine.

As her father led Britain’s fight against Nazi Germany during World War II, she joined first the Red Cross and later military units. She served in London, Belgium and Germany with anti-aircraft batteries of the army’s Auxiliary Territorial Service.

She also accompanied her father on several of overseas journeys, including the postwar planning conference in Potsdam, Germany, attended by U.S. President Harry S. Truman and Soviet leader Joseph Stalin.

After the war, she married Conservative politician Christopher Soames, becoming Lady Soames when he was made a peer. Her husband died in 1987.

Lady Soames wrote several books about her family, including a well-received biography of her mother, and was a patron of many nonprofit groups.

Survivors include five children, including Nicholas Soames.