The Duke of Westminster, Gerald Cavendish Grosvenor, died aged 64 on Tuesday after suddenly becoming ill, his family said.
His son, Hugh, has inherited the £9bn dukedom which has been described as equivalent owning "half of London".
The family can trace a lineage for nearly a millenia and to the creation of the title Duke of Westminster, back in 1874 as well as Baronets of Eaton prior to that as far back as 1622.
As a result, much of the family's wealth is inherited and tied up in a property development company worth £12.5bn.
When he was once asked by the Financial Times what he'd advise young entrepeneurs to do to emulate his riches, he replied with:
Make sure they have an ancestor who was a very close friend of William the Conqueror.
Oh. Ok then.
HT Katie Martin