Grigson was born Heather Mabel Jane McIntire on 13 March 1928 in Gloucester, Gloucestershire, the daughter of George and Doris McIntire. George was a solicitor and the deputy town clerk of Gloucester; Doris was an artist. Grigson later said that home was where she "first learnt about good English food". After he had been involved in the closure of an abattoir, George gave up eating meat. When Grigson was four the family moved to Sunderland, North East England. She picked up a trace of a north-east accent that remained with her, and what the "Oxford Dictionary of National Biography" calls a "quietly left-wing" political viewpoint. During the Second World War, Sunderland was a target of "Luftwaffe" bombs, so Grigson and her sister Mary were sent to Casterton, a boarding school in Casterton, Cumbria. She then gained a place at Newnham College, Cambridge to read English literature.