Dowager Duchess of Northumberland

The Dowager Duchess of Northumberland, who has died aged 90, was a Scottish aristocrat whose marriage to Hugh Percy joined together two of the most illustrious families on either side of the Border.

Born Lady Elizabeth Diana Montagu Douglas Scott, she was the first child of Walter, Earl of Dalkeith, later to become the 7th Duke of Buccleuch, and Mollie Lascelles. Both her parents were descendants of Charles II.

Her early years were spent at Eildon Hall, near St Boswells. When in 1935 her father succeeded to the Buccleuch title, the family moved in to Drumlanrig Castle. She also spent a great deal of time in several other great homes which the new duke inherited, notably Bowhill near Selkirk and Boughton in Northamptonshire.

After receiving her education at home, Lady Elizabeth travelled to France, Italy and Germany to study languages. It was while in Italy that she witnessed a meeting between Hitler and Mussolini, "two unattractive stout little square men" as she later described them.

As the prospect of war increased, she returned to Britain in May, 1939 and took part in the final debutante season before the conflict broke out. In the early years of the war she worked on the Buccleuch estate and, after successfully completing a first aid course, she joined the Civil Nursing Reserve, serving in a Dumfries hospital.

She then decided to sign up for active service, travelling to London where she joined the Women's Royal Navy Service in 1943. She qualified as a decoder rating and, declining a commission, accompanied three other Wrens on a voyage to New York aboard the Mauretania. Under constant threat from German U-boats, she returned on the ship to Liverpool with 8000 US troops on board. She later sailed to Boston and Nova Scotia. Then in 1944, by now an officer, she was dispatched to Australia. Lady Elizabeth had always considered herself a dull, shy country girl but, by the end of the war, she had become an adventurous, charming and independent young woman.

In 1946 she married Hugh Algernon Percy, the 10th Duke of Northumberland in what was the first big post-war society wedding, attended by King George, Queen Elizabeth and the two young princesses, Margaret and Elizabeth.

The new Duchess moved from Buccleuch to the equally splendid Alnwick Castle which, much later, would feature as the Hogwarts school in the first two Harry Potter movies. Her husband played a prominent role in Northumberland, serving as a county councillor for two decades, chancellor of Newcastle University and Lord Lieutenant for many years.

The duchess also became keenly involved in her local community, working for a number of community organisations including the Red Cross and a variety of hospices and charities.

After the duke's death in 1988, the duchess moved in to Friar's Well, a property in Alnwick designed for her by Sir Hugh Casson. However, in her later years she spent much of her time at Albury, the family estate in Surrey. It was there that she died after a walk in her beloved garden.

The Dowager Duchess is survived by two sons, Ralph, the 12th Duke of Northumberland, and Lord James Percy, and three daughters:Ladies Caroline Mary, Victoria Lucy and Julia Helen. Their eldest son, Henry, Earl Percy, who succeeded his father as the 11th Duke, died after an accidental overdose of prescription drugs in 1995, and fourth daughter, Lady Louise Percy survived only two days after her birth in 1962.