Simon was born in Hampstead in London, the son of Claire and Frank Cecil Simon. His father was a stockbroker. He was educated at Gresham's School, in Holt, Norfolk and read English at Trinity Hall, Cambridge. He was elected an Honorary Fellow of Trinity Hall in 1963. He was called to the bar at Middle Temple in 1934, and joined the chambers of Tom Denning (later Lord Denning MR), practising mainly in family law and trust law.
