[3] Aggrieved by the attitude of the Head Master, Dr. Henry Ingles (1794–1806), following the breaking of a window, students blew his classroom door off with gunpowder and followed this by burning desks and books[4] upon the close, before retreating to the Island (a Bronze Age burial mound surrounded by a moat).

Cotton was appointed Adjutant-General to the reserve under the Command of Arthur Wellesley (soon to become the Duke of Wellington) and was involved in the Battle of Køge on 29 August 1807.

[5] Cotton was deployed to the Iberian Peninsula in April 1809, where he served as Adjutant-General to the Light Division under Brigadier-General Robert Craufurd.

Cotton was present throughout the retreat to the lines of Torres Vedras and subsequent advance, seeing action at the Battle of Côa.

He was involved in the Siege of Bayonne and commanded the piquets of the Second Brigade of Guards on the night of the French Sortie, 14 April 1814.

He became the Lieutenant-Governor of Plymouth and General Officer Commanding Western District in 1835[9] and was Commander-in-chief of the Bombay Army from April 1847 until he retired in December 1850[10] and was invested as a Knight Grand Cross, Order of the Bath.