He was an heir to the Hambros Bank. His great-great-grandfather, Carl Joachim Hambro, was an immigrant to England from Denmark who founded the Hambros Bank in 1839. His father, Sir Charles Jocelyn Hambro, was a merchant banker who was descended from Robert the Bruce. His mother, Pamela Cobbold, of the East Anglian brewing family, who also claimed royal descent via George Keppel, 3rd Earl of Albemarle, died when he was 21 months old. He grew up at Delcombe Manor in Dorset.