Most Searchlight Regiments were originally raised as either Anti-Aircraft Battalions, Royal Engineers or by converting Infantry Battalions within their own regiments. The Infantry Battalions remained part of their parent regiment but carried the RA Searchlight Regiment title in brackets after their title e. g. 2/5th BattalionThe Durham Light Infantry (55 Searchlight Regiment)(TA).
In mid 1940 these units were all re-designated Royal Artillery.