Hugh Grosvenor, the 7th Duke of Westminster, inherited his title at just 25 years old. Today, the Duke of Westminster and the Grosvenor family are worth billions, making them one of Britain’s wealthiest aristocratic families.

The roots of that fortune stretch back to 1677, when Sir Thomas Grosvenor married Mary Davies. Her inheritance included hundreds of acres of land west of what was then London.

At the time, much of it was countryside. London grew.

Over the following centuries, the Grosvenor family developed parts of the land into Mayfair and Belgravia, neighborhoods that became some of the most valuable real estate in the world. The family’s holdings have since expanded far beyond London through the Grosvenor property business.

Hugh Grosvenor became the 7th Duke of Westminster in 2016, following the death of his father. The title dates only to 1874, but the land behind much of the family fortune has been in the family for centuries.

It may be one of history’s better examples of the old real-estate rule: location, location, location.