Mary, Marchioness of Ailsa; Born May 3, 1916; Died August 17, 2007. THE long life of Mary, Marchioness of Ailsa, who has died aged 91, was inextricably bound up with Culzean Castle, the Kennedy family seat until the house and its contents were handed over to the National Trust for Scotland in 1945.

Lady Ailsa was one of the last members of the Kennedy family to live at Culzean, which dominates the South Ayrshire coastline, along with her late husband the 7th Marquess, Archibald David Kennedy. She lived in Ayrshire for most of her life, latterly at Cassillis.

One of Scotland's most visited stately homes, Culzean had a heritage that was zealously guarded by Lady Ailsa following her husband's death in 1994. A slender lady with an aristocratic air, she was particularly forceful in the face of several controversial alterations to the castle's collection of furniture and pictures.

Lady Ailsa always proclaimed: "I am proud of being a Kennedy", the family of which she was a member for more than half a century. Born Mary Burn in 1916, the youngest of eight children, she never knew her father John, who was killed in France towards the end of the Great War. At the Duchess School in Alnwick, young Mary excelled on the sports field and led a happy but frugal home life with her widowed mother.

During the Second World War, she ran the office for the land girls under Sir John Craster. She later joined the then WVS to look after soldiers' welfare and, following training in London, was posted to Germany in the late 1940s, where she spent two happy years. Not wishing to leave her mother, she turned down a post in Hong Kong.

Thereafter, Mary was posted to Strathpeffer in the Highlands to supervise the welfare of soldiers' families. At a New Year's Eve Ball she met David Kennedy, then Earl of Cassillis, who was learning estate management on the Fairbairn Estate. They married in 1954, nine years after his uncle, the 5th Marquess, had gifted Culzean Castle to the National Trust, for which her husband later worked at Inverewe Gardens in Wester Ross.

Initially living there, they soon moved to the new wing at Culzean Castle, and from there to Cassillis, where Mary restored the neglected house and gardens - known as The Jungle - a project which benefited from her love of nature.

The marriage produced two sons, the 8th Marquess, Archibald Angus Charles Kennedy (born 1956), and his brother Lord David Thomas Kennedy (born 1958), and also one daughter, Lady Elizabeth Helen Kennedy (born 1955). The 5th Marquess died in 1956, and within a day of completing his first year as the 6th Marquess, Angus Kennedy died in 1957. Thus Mary became Marchioness of Ailsa and her husband the 7th Marquess.

These were busy and enjoyable years. The top floor of Culzean had been gifted to General Dwight Eisenhower as a thank you from the people of Scotland for his wartime service and Lady Ailsa acted as hostess to the former President on at least one occasion.

Known locally as "the Marchioness", Lady Ailsa's vibrant personality meant she was much in demand for speaking engagements. The Ayrshire Hospice was close to her heart, while she was also appointed an Honorary Commandant of the Girls Venture Corps, an Honorary President of Turnberry Ladies Golf Club, and an Honorary President of Ayr Choral Union. Herself a gifted musician, she was an accomplished pianist with a fine singing voice.

Lady Ailsa shared President Eisenhower's dedication to Maybole, enthusiastically supporting celebrations in September 2005 to mark the 60th anniversary of the end of the Second World War and the handing over of Culzean Castle. At the 1945 VE Day celebrations in a marquee on the castle lawn, she led off the dancing in grand fashion.

The 7th Marquis died on their 40th wedding anniversary in 1994. Lady Ailsa is survived by her daughter, two sons, and two grand-daughters, Lady Rosemary and Lady Alicia.