Hartnell left school without prospects and dabbled in petty crime. At the age of 16, he met the art collector Hugh Blaker, who later became his unofficial guardian, arranged for him to train as a jockey, and helped him to enter the Italia Conti Academy. Theatre being a passion of Blaker's, he paid for Hartnell to receive some "polish" at the Imperial Service College, though Hartnell found the strictures too much and ran away. When Hartnell married, he and his wife continued to live in one of Blaker's adjacent properties at Isleworth and their daughter was born there in 1929.