The unit was formed on 1 November 1938 by converting the 7th (23rd London) Battalion, East Surrey Regiment, a Territorial Army (TA) infantry battalion, into a tank unit.

For a short while it was 42nd (7th (23rd London) Battalion, East Surrey Regiment) Battalion of the Royal Tank Corps before the corps was redesignated the Royal Tank Regiment in 1939.

[4] The unit formed part of 1st Army Tank Brigade in 1941–42, serving with it in the Western Desert Campaign including the Second Battle of El Alamein.

[5] For the invasion of Northern Europe in 1944, it was equipped with Canal Defence Light Grant tanks.

[citation needed] From 1947, when the TA was reconstituted, the regiment was in 22nd Armoured Brigade under the 56th (London) Infantry Division.