Born: December 22, 1951;

Died: August 9, 2016

THE sixth Duke of Westminster, who has died aged 64, was an aristocrat and landowner who was said to be worth some £8.3 billion, making him the 68th richest billionaire in the world, and third in the UK. He owned 190 acres in Belgravia, adjacent to Buckingham Palace and one of London's most expensive areas, as well as thousands of acres in Sutherland.

He was not always comfortable with his wealth and privilege though. He only realised that he would inherit his great wealth when he was 15 years old and originally wanted a career in the Armed Forces. However, by his early 20s, on becoming trustee of the estate, he was forced to abandon the idea – although he did satisfy his love of all things military by serving in the Territorial Army, rising to become a colonel.

He became the sixth Duke of Westminster at 27, and credited himself with using his vast wealth responsibly – he supported a great number of charities and good causes particularly in rural and inner-city areas with links to his estate – although he once said that he sometimes wished he had not been rich. "Given the choice,” he said, “I would rather not have been born wealthy, but I never think of giving it up. I can't sell. It doesn't belong to me."

A close friend of the Royal Family and Prince Charles’s best friend, the sixth Duke was known for taking his responsibilities as one of Britain's wealthiest men and biggest landowners seriously, although he was also a private man who defied expectations and regularly spoke out on controversial issues.

Born in 1951, Gerald Cavendish Grosvenor grew up in Northern Ireland and was educated at Harrow, where he gained two O-levels, and later went to work on ranches in Australia and Canada.

He then served an informal apprenticeship in property management with a Mayfair estate agent and on the Duke of Buccleuch's 300,000-acre Dumfriesshire estate.

In 1973, when he was 22, he became trustee of the Grosvenor Estate and was forced to abandon his dream of a career as a professional soldier in his uncle's regiment, the 9th/12th Lancers. He instead signed up to the Territorial Army and in 1994 received an OBE for his work as a volunteer soldier.

When his father Robert died in 1979, he became the sixth Duke of Westminster. He also succeeded his father to become chairman of Grosvenor Holdings, the commercial arm of the Grosvenor Estate, and dedicated himself to using his wealth responsibly.

The Westminster Foundation, which manages the estate's charitable giving, has donated to more than 1,500 charitable organisations since 1974, and the Duke was also president of the RNIB for 25 years and president of the St John Ambulance for 10 years. He made a £500,000 donation to farmers during the 2001 foot-and-mouth outbreak.

However, as an outspoken member of the aristocracy, the Duke was also given to acts of non-conformism. An advocate of change in the Lords, he quit the Conservative Party in 1993 after it proposed the Bill on Leasehold Reform, which would have had a huge effect on his massive London landholdings.

He also paid thousands of pounds to some of his workers to help them meet the poll tax - which he described as insufferable.

The Duke once said that his life would have been easier if he had sold his estate to live in the Bahamas, but said that would not have been the responsible thing to do.

In 2000, he spoke for the first time about suffering a nervous breakdown and the cloud of depression which overcame him in 1998 after the pressures of businesses and making 500 public appearances a year overcame him.

Having grown up in Northern Ireland where the nearest town, Enniskillen, was seven miles away, he always considered himself a country person by birth and inclination and saw himself as a protector of it for future generations. "Nature is holistic," he said. "We as homo sapiens are no more important than the deer in the park. We are living together and we depend on each other. We have got to treat our countryside better. We think, in our arrogant fashion, of homo sapiens as being the dominant species. This is wrong. We are only dominant because we invented gunpowder and the JCB and the blasted motor-car. We are not dominant over nature. We must never take that view. All our efforts to control nature will prove futile."

His family life has been notably private. The Duke married Natalia Phillips in 1978 and they have one son and three daughters. His wife is a godmother to the Duke of Cambridge and his only son Hugh, is Prince George's youngest godfather.

He also spoke publicly about wanting to ensure his own children were instilled a commitment to using their wealth responsibly.

Speaking about his son and heir Hugh in 1993, he said: "He's been born with the longest silver spoon anyone can have, but he can't go through life sucking on it. He has to put back what he has been given."

The Duke died on Tuesday after suddenly becoming ill. He had been transferred from his Abbeystead Estate in Lancashire to the Royal Preston Hospital, where he died. The Prince of Wales and Duchess of Cornwall said they were deeply shocked and saddened by the sudden death.

The Duke of Westminster is succeeded by his son and is survived by his wife, and daughters Lady Tamara, Lady Edwina and Lady Viola.