The new seventh Duke of Westminster is only 25 years of age, a godfather to Prince George and now "owns half of London".
The death of the sixth Duke of Westminster, Sir Gerald Cavendish Grosvenor, on Tuesday means his £9.9 billion estate has passed to his only son, Hugh, who is two years younger than his father when he took on the title and land aged 27.
Described as "baby-faced" and "absurdly rich" by Vanity Fair, the account manager for a green tech company is now the third richest person in the UK and 68th richest in the world, according to Forbes.
- Partly state-educated but lavish in lifestyle
Although he began his education at a state primary school and went on to study countryside management at Newcastle University, the former Earl Grosvenor was hardly protected from his family's wealth.
Four years ago he threw a £5 million party to celebrate his 21st birthday, with Prince Harry among 800 guests donning "black tie and neon" and bringing a bottle of wine to the bash.
Comedian Michael McIntyre and the hip hop duo Rizzle Kicks provided the entertainment at Eaton Hall, the Grosvenor family's country seat in Cheshire.
- 'Goes wild for girls in neon'
The lavish celebrations led the Tatler List to gush over the eligible future billionaire bachelor, whose full name is Hugh Richard Louis Grosvenor, as someone destined to "own half of London".
"Hughie's a Newcastle graduate with his own wine collection who goes wild for girls in neon."
- Male inheritor despite older sisters
Although Hugh is the third of his father's four children, the common law of primogeniture (the right of the firstborn male child to inherit a family estate) means the fortune passes to him rather than his two elder sisters.
The family's estate, which dates back to the 15th century, includes 300 acres in Belgravia and Mayfair - two of London's most exclusive areas - as well as thousands of acres in Scotland and Spain.
- Close relations with royalty
His naming as Prince George's youngest godfather in 2013 by the Duke and Duchess of Cambridge continued his family's close relations with the royals.
Hugh's mother Natalia, the Duchess of Westminster, is one of the Duke of Cambridge's godparents, while one of his three sisters, Lady Tamara, is married to Edward van Cutsem, whose brother William van Cutsem is also a godparent of Prince George.
His late father, who died unexpectedly on Tuesday afternoon at the age of 64 after falling ill on his Abbeystead Estate, was a close friend of the Prince of Wales and Duchess of Cornwall.
- Philanthropic duties
Hugh is likely to have to take on responsibility for the Westminster Foundation, the charitable body which manages the philanthropic activities of the Grosvenor family.
It was set up in the 1970s and since then has awarded over £40 million in grants.
Although missing out on the family fortune, Hugh's sisters are reportedly set to inherit what the Daily Mail described as "considerable trust funds".
- Who are Britain's five wealthiest people?
- The top 10 is completed by:
- 6. Tavistock group chairman and Tottenham Hotspur owner Joe Lewis (£4.06bn)
- 7. Property developer brothers Ian and Richard Livingstone (£3.9bn)
- 8. Identical twins Sir David and Sir Frederick Barclay, who own hotels including London's Ritz as well as the Telegraph Media Group (£3.76 bn)
- 9. Sir Richard Branson, high-profile owner of the Virgin brand (£3.76 bn)
- 10. Laurence Graff and family, who own Graff Diamonds (£3.5bn)