On 2 March 1950 – less than a month before his thirty-eighth birthday – Cub was sworn in as a Member of Parliament. However, he had yet to reach the House of Commons: this was still being restored after war damage, so the MPs gathered in the “gothic splendour” of the House of Lords. At first Cub was uneasy in his seat; for some reason, at the start of every day's proceedings he “felt a slight quiver of apprehension – since it must, I thought, be a dream – that some burly Door-Keeper would tap me on the shoulder, seize me by the scruff of my neck and [drag] me through the great brass doors”.

Cub was one of 93 Conservative MPs who had never sat in Parliament before; perhaps he was not the only person to think that his presence was a mistake which would soon be ended by a doorkeeper's hand on his collar. But he belonged to what even Nye Bevan admitted was “the finest Tory vintage in history” – Cub attributed its quality to the maturity which most had gained from war service – and soon the newcomers were playing a full part in what turned out to be a Parliament of only 20 months. On 14 March Iain Macleod delivered his maiden speech, on the National Health Service budget, and two days later Enoch Powell spoke on a Defence White Paper. Cub's opportunity came during a debate on the Army Estimates on 20 March.