Surgeon and journalist. Educated at Christ’s Hospital (where he was a contemporary of Samuel Taylor Coleridge and Charles Lamb) and University College, Oxford (BA 1796, MA 1803, MB and MD 1803). He first met Southey, who was flirting with a career in medicine, at the Anatomy School in Oxford in early 1794. They became firm friends, Southey later describing how in 1794 Allen had been his ‘bosom-companion’ and had ‘rendered many hours delightful which would otherwise have passed in the destructive daydreams of solitude’. Allen wrote poetry and, in Oxford in June 1794, introduced Southey to Coleridge. In 1794–1795, Allen was possibly a convert to Pantisocracy. In 1796, he enrolled at the Westminster Hospital and married a wealthy widow, Catherine, daughter of Nathaniel Forster (1726–1790; DNB). She died within a year. In 1797, with the encouragement of Anthony Carlisle, he became deputy surgeon with England’s Second Royals, then stationed in Portugal. He was back in Britain by 1802 and from 1803 until his death worked as a journalist, writing for (according to Charles Lamb) the London newspapers the Oracle, True Briton, Star and Traveller.