Henry Tonks, FRCS (9 April 1862 – 8 January 1937) was a British surgeon and later draughtsman and painter of figure subjects, chiefly interiors, and a caricaturist.

[2] At the start of the 1907-08 academic year Tonks appointed Derwent Lees (initially one day per week as he was still a Slade pupil) as his Assistant in Drawing, a position he held until 1918.

[3] Other pupils of Tonks at the Slade included Winifred Knights, David Bomberg, Mark Gertler, Harold Gilman, Spencer Gore, Augustus John, Gwen John, Percy Wyndham Lewis, William Orpen,[4] William Roberts, Isaac Rosenberg,[5] Stanley Spencer, and Rex Whistler.

He served as a medical orderly at a British Red Cross hospital near the Marne in France in 1915, and joined an ambulance unit in Italy.

He became a lieutenant in the Royal Army Medical Corps in 1916, and worked for Harold Gillies producing pastel drawings recording facial injury cases at the Cambridge Military Hospital in Aldershot and the Queen's Hospital, Sidcup[9][10] – a contribution recognised in the exhibitions Faces of Battle at the National Army Museum in 2008 and Henry Tonks: Art and Surgery at the Strang Print Room of University College London in 2002.

In August 1918, they both witnessed a field of wounded men near Le Bac du Sud, Doullens, which became the basis for Sargent's vast canvas, Gassed.

tall, lean and ascetic looking, with large ears, hooded eyes, a nose dropping vertically from the bridge like an eagle's beak and quivering camel-like mouth".