Wife of Margaret Thatcher's right-hand man Willie Whitelaw;

Born: January 1, 1917; Died: December 5, 2011.

LADY Celia, Viscountess Whitelaw, who has died aged 94, was best-known as the self-effacing but staunchly supportive wife of William "Willie" Whitelaw MP, former Home Secretary, Deputy Prime Minister and trusted aide of Margaret Thatcher.

But she was highly active in her own right, campaigning for her husband and the Conservatives and supporting countless charities, not least in Cumbria where she and her husband spent much of their lives when he was MP for Penrith and the Border.

From their long-time country home, Ennim, outside the village of Great Blencowe near Penrith, she worked for the Cumbrian branch of the Barnardo's children's charity, the Women's Institute, the British Red Cross (she was its president in Cumbria), the Eden Valley hospice in Carlisle for those with terminal or life-limiting illnesses, and the Yellow Brick Road Appeal of the Children's Foundation. She was also a devoted and gifted gardener and a lover of dogs and thoroughbred horses, a life-long follower of the Cheltenham Festival and a member and familiar figure at Carlisle race course.

While her fiancé and later husband was fighting in the Second World War as a major in the Royal Scots Guards – where he won an MC for bravery – young Cecilia (her birth name, although it later got shortened to Celia) did her bit for the war effort at home, serving as a clerk for the women's Auxiliary Territorial Service (ATS) .

Cecilia Doriel Sprot was born in the family mansion on the Riddell Estate, Lillisleaf, near Melrose, to Major Mark Sprot of the Royal Scots Guards and Meliora Hay. She was brought up to the sound of hooves and the shooting of pheasants and partridge. Her primary schooling was from governesses at home but she finished her education at the newly opened Oxenfoord Castle girl's boarding school at Pathhead, Midlothian, now a venue for weddings and events.

From the age of nine, she had known a boy called William Whitelaw, who, although he was born in the north-east of Scotland, was a regular visitor to his family estates farther south and later a regular invité to shoot or attend her mother's tea parties in the Riddell mansion house.

Along with her childhood friend and fellow land-owning Scottish Borderer Meg Egerton (later Lady Meg Colville), she volunteered for the women's ATS in Kelso. Fitted out with tailored uniforms, the two young debutantes were posted to Edinburgh Castle as clerks at the ATS Scottish Command. The friends would later lead the ATS along Princes Street to the Mound on VE Day. Their exploits were mentioned in the book Debs at War 1939-1945: How wartime changed their lives, by Anne De Courcy.

While on leave from the frontlines, Willie Whitelaw re-met his wife-to-be, they got engaged in 1942 and married in St Giles Cathedral, Edinburgh, on February 6, 1943.

After the war she played an active role in helping him run his family estates in Dunbartonshire and Lanarkshire. When he decided to go into politics in the 1950s, she became a campaigner and active parliamentary wife.

She was by his side when he won the seat for Penrith and the Border in 1955, a seat he held for nearly 30 years. She was by his side when he was named Captain of the Royal and Ancient in 1969. She was never far from his side when he was in the Cabinet, including as the country's first Northern Ireland Secretary under Edward Heath, later deputy and right-hand man to Mrs Thatcher, who once said: "every prime minister needs a Willie."

When he became Viscount Whitelaw in 1983, she became Viscountess Whitelaw of Penrith.

After her husband suffered a series of strokes from 1987, she cared for him. When he died in 1999, she sold Ennim and moved to be closer to her daughter, Mary, and brothers, Jock (who died last year aged 99) and Aidan, now 92.

Viscountess Whitelaw died in Edinburgh and is survived by her daughters Elizabeth, Carolyn, Mary and Pamela and 12 grandchildren, as well as her brother Aidan.