The Duke of Devonshire, one of Britain's wealthiest landowners and whose vast Chatsworth estate is one of the most visited in the country, has died aged 84.

Andrew Robert Buxton Cavendish was the 11th Duke of Devonshire. The title dates back to 1694 and many of its holders have been prominent politicians, including one prime minister, one leader of the Liberal Party, and one governor-general of Canada.

The duke himself served as a minister - in colonial affairs and Commonwealth relations - in the Conservative government of his uncle, Prime

Minister Harold Macmillan, between 1960 and 1964.

Around the estate, in the centre of the Peak District National Park, the duke was known as an easy-going and unstuffy man. He opened Chatsworth to the public in the 1950s and, with his wife Deborah, made it a thriving business, attracting a half-million visitors a year to its art collections and acres of parkland. The house, largely built at the end of the seventeenth century in place of an Elizabethan building, is surrounded by 35,000 acres of estate land.

The duke had an estimated personal wealth of between (pounds) 500m and (pounds) 1.6bn. He was Britain's 73rd richest person in the latest Sunday Times rich list, but his art collection alone is estimated to be worth in the region of (pounds) 800m.

The duke and duchess kept up the family tradition of collecting and commissioning works of art, including paintings by Lucian Freud, sculpture by Elisabeth Frink and Angela Conner, and outstanding books and mineral specimens. In addition to Chatsworth, the family property includes Bolton Abbey in North Yorkshire, two hotels and Lismore Castle in County Waterford, one of Ireland's finest castles.

Born in 1920, he was educated at Eton and at Cambridge University. He was the second son of the 10th duke, the MP for West Derbyshire and a member of Winston Churchill's war cabinet. His elder brother, William, who was married to US President John F Kennedy's sister Kathleen, was killed in action in 1944, so when their father, the 10th duke, died in 1950, Andrew became the 11th duke.

In 1941, he married Deborah, one of the famously unconventional Mitford sisters - who included writers Nancy and Jessica Mitford and Lady Diana Mosley, wife of Britain's pre-Second World War fascist

leader Sir Oswald Mosley.

With the estate, where the Cavendish family had lived for four centuries, came an estate-tax bill for (pounds) 7m. The new duke and duchess survived the financial crisis by selling

family treasures and turning Chatsworth into one of the country's most popular attractions. With 297 rooms, 1.3 acres of lead roof and 105 acres of gardens, it is an expensive place to keep. The estate now has a hotel, a garden centre, a farm shop selling meat and produce from its own farm, and sells merchandise on the internet.

The duke served in the Coldstream Guards throughout the Second World War. He was awarded the Military Cross for distinguished service in battle in Italy, yet he told a news-paper last year that he had won his medal for ''being cheerful''.

He was also quoted as saying he believed Chatsworth would go down in history as ''the home of a very dim family, nothing more''.

Once asked by his estate workers when he planned to retire, he answered: ''I've never worked a day in my life, so how can I retire?''

Before succeeding to the title, the duke unsuccessfully contested two parliamentary elections in Chesterfield and served briefly as mayor of Buxton.

A keen fox hunter, the duke also retained a lifelong interest in horse-racing. Park Top gave the duke a day to remember in 1969 when Lester Piggott rode her to victory in the King George VI And Queen Elizabeth Diamond Stakes at Ascot. She also beat many of Europe's leading colts when successful in the Coronation Cup that year, as well as in the Hardwicke Stakes at Royal Ascot.

His other sporting interest was the local football team in nearby Chesterfield. Second division Chesterfield FC will hold a minute's silence before their last game of the season this Saturday at home to Luton Town as a mark of respect to the duke, who was the club's president.

Club chairman Barrie Hubbard said: ''His Grace, the Duke of Devonshire was club president for nearly 50 years and has always kept a healthy interest in the fortunes of the club.

''He was with us when the club received the freedom of the borough of Chesterfield for the historic FA Cup run in 1997 and then was especially helpful when the club was in serious financial difficulties in recent years.''

A distant cousin of the Queen, the duke was a close friend of the Prince of Wales, who was a regular weekend

visitor to Chatsworth, along with his partner, Camilla

Parker Bowles.

The duke was also known for charitable work, and for his self-effacing manner. He supported the London Library for years and was president of

the RNIB, the National Association for Deaf Children,

Mencap, as well as many other

Derbyshire charities.

The duke and duchess had three children: Lady Emma, Lady Sophia and Peregrine, the Marquis of Hartington, who succeeds his father as 12th Duke of Devonshire.

Andrew Robert Buxton Cavendish, 11th Duke of Devonshire; born January 2, 1920, died May 3, 2004.