Granville was Liberal MP for the Eye Division of Suffolk from 1929-1951 and one of three Liberal MPs in the 1950-51 Parliament who set out to reassert the ‘radical tradition’ of the Liberal Party – the others were Lady Megan Lloyd George (Anglesey) and Emrys Roberts (Merioneth). All three lost their seats in 1951; Lady Megan also later defected to Labour and Roberts largely withdrew from political life. Granville narrowly failed to regain Eye as a Labour candidate and later became a Labour peer.