He died suddenly after suffering a heart attack at his estate in Lancashire in north-west England.

The vast bulk of that fortune comes from his ownership of much of the swanky London quarters of Mayfair and Belgravia, once the stamping ground of the native upper classes, but now more associated with the international uber-rich, the hedge fund industry and–at least until the new one is ready–the U.S. Embassy (which stands in a square named after his family). In the real-life British version of the board game Monopoly, the Grosvenor family, to all intents and purposes, own the dark blue bits (and we all know how that one plays out).

The value of those land-holdings allowed the 6th Duke to escape the inevitable economic decline of his peers in the aftermath of two world wars. Prime central London real estate has been one of the best performing of all asset classes for the last 40 years, although uncertainty ahead of the U.K.’s referendum to leave the EU has dealt it a rare setback: average land values were down 9.4% on the year at the end of the second quarter, according to a report by realtors Knight Frank.

The duke had thrown himself into the real estate business at an early age, the better to understand and manage the source of his wealth. Over the years, his holding company, Grosvenor Estate, expanded internationally, with projects from Hong Kong to Vancouver. It mourned him Wednesday as “a passionate country man, committed soldier, an excellent shot, a true entrepreneur and, importantly, he went out of his way to be courteous and humorous with all people, regardless of status or wealth.”

The last attribute is illustrated by an anecdote published in London’s Evening Standard Wednesday. Dropping in on the now-defunct Westminster Press , he chose the wrong moment to express an interest in the photos department and retreated, smiling and unruffled, when told to “f— off out of my dark room” by a stressed editor.

For most of his adult life, his chief passion in life was the Queen’s Own Yeomanry, the reserve army regiment that he rose to command. He served for four years as assistant chief of defense staff, responsible for reserve and cadet units, but stepped down in 2007 after being named as a client of the escort service Emperors Club VIP, in the scandal that also brought down former New York Governor Eliot Spitzer.

An arch-typical blue-blood in some ways, he was still impossible to pigeon-hole. He left the Conservative Party in 1993 in a row over proposed reforms of property lease laws, and he had personally picked up the bill for many of his employees when Margaret Thatcher introduced the much-hated and short-lived Poll Tax a few years earlier.

Most sacrilegiously of all, he initially wanted to become a professional soccer player and was offered a trial at Fulham FC in London (this at a time when he was not in line to succeed to the duchy, and before mediocre soccer players commanded salaries in line with the income of most aristocratic estates).

As is usual for the British aristocracy, the estate will pass more or less in its entirety to the 7th duke, the (unmarried) 25 year-old Hugh.

Although his record as a landlord was a solid one, His Grace never suffered from any illusions about his business acumen. The Financial Times once asked him what advice he would give to young entrepreneurs. “Make sure they have an ancestor who was a very close friend of William the Conqueror,” came the reply.