Gemma Jones was born on 4 December 1942 in Notting Hill, London, the daughter of the Anglo-Welsh actor Griffith Jones. Her paternal grandfather was a Welsh-speaking dairy owner and former lead miner, giving her a family connection to Wales going back a generation further, though she herself was raised in London. Family accounts describe an old family cottage near Aberystwyth and some knowledge of spoken Welsh, though these details are not independently verifiable.
Jones has had an extensive and distinguished career on stage, television and film, earning three BAFTA TV nominations. She is perhaps best known to cinema audiences as Mrs Jones in the Bridget Jones film series and as Madam Pomfrey in Harry Potter and the Chamber of Secrets. Her television work includes the BBC series Spooks and an appearance in the very first episode of the classic police drama Z-Cars.