 Trimble was commissioned lieutenant in the 15th Lancashire AVC on 13 December 1862, promoted to captain on 2 July 1863, and became Lieutenant-Colonel in command.Mewburn returned to the command with the rank of Lt-Col on 23 February 1875 after Trimble resigned to emigrate to New Zealand, whereupon Trimble became the first Honorary Colonel of the unit.Mewburn retired on 19 April 1890. and H.J.