The writer is group chief executive of Nesta, a UK innovation charity

When my father was orphaned after fleeing on foot from Myanmar (then Burma) to Chennai during the second world war, he had to borrow a rupee from his uncle just to sit a school entrance exam. What propelled him into the medical career that eventually brought him to England was not just academic talent or a good school — it was becoming best friends with two boys from a higher caste and class, both determined to become doctors. As he tells it, their confidence and ambition became his.

Friendships can change your life — particularly those that span class boundaries and expand horizons. I have seen the power of such friendships in my own family. But while the impact of friendship on social mobility has long been theorised, only recently has it become possible to test empirically. Large-scale data allows us to measure what was once mere anecdote. Harvard professor Raj Chetty’s US research shows that one of the strongest predictors of upward mobility is having friends from higher-income backgrounds — he calls this “economic connectedness”.