I grew up in a mining area in the north east. Not a poor background but parents never had much money. I was the clever kid in school, worked my socks off and got a law degree from cambridge. Then moved to London for work.
I thought that law firms would be full of people like me and some posh people. In my office I’d say a an overwhelming majority of people come from what I’d consider a posh background - parents who are professors, diplomats, barristers, partners at law firms, senior accountants etc.
People who grew up privileged, good private schools, academic households, then onto a top uni.