The battery was formed on 1 February 1805 as I Troop, Horse Artillery at Colchester, Essex as a horse artillery battery of the British Army. Captain Robert Bull was appointed to command and he took it to the Iberian Peninsula in August 1809 where it served until 1814. It arrived too late for the Battle of Talavera, but thereafter took part in most of Wellington's major actions of the Peninsular War including Bussaco (1810), Fuentes de Oñoro (1811), Ciudad Rodrigo, Badajoz, Salamanca, and Burgos (1812), Vitoria, San Sebastián, the Bidassoa and the Nive (1813) and Bayonne (1814).