Baroness Howard de Walden and family
Rank 2017

The Howard de Walden family's 92-acre London estate, which includes the world-famous medical clinics of Harley Street, has been transformed in recent years, with Marylebone High Street regarded as one of the capital's most fashionable shopping areas. The family is led by the 81-year-old 10th Baroness, the eldest of four daughters of Lord Howard de Walden, who died in 1999. All four sisters sit on the board, overseeing an estate that has been in family hands since 1879 and comprises about 850 buildings. Central London's property prices are holding up well and we value the family's business assets at £3.5bn, adding £230m for other wealth.