Sir Percival Hartley CBE MC FRS[1] (28 May 1881 – 16 February 1957) was an English immunologist who was head of the Medical Research Council (MRC) Biological Standards Division for 44 years.

[3][2][4][5][6] Harvey was born at Calverley, Yorkshire, England, the son of William Thompson Hartley, a coal merchant.

[1] He was educated at Belle Vue School and attended Bradford Technical College and then the University of Leeds where he studied chemistry, qualifying BSc in 1905.

At the outbreak of the First World War, he joined up with the Royal Army Medical Corps (RAMC) and served as a captain from 1915 to 1919, winning the Military Cross in 1917.

[1] Hartley then worked for two years at the Wellcome Physiological Research Laboratories, where he developed a culture broth that permitted reliable production of diphtheria toxin.