The unit was formed by converting the 7th (23rd London) Battalion of The East Surrey Regiment, a Territorial Army infantry battalion, into a tank unit. For a short while it was 42 (7 (23 London) Battalion The East Surrey Regiment) Battalion of the Royal Tank Corps before becoming part of the Royal Tank Regiment in 1939 The unit formed part of 1st Army Tank Brigade. For the invasion of Northern Europe in 1944, it was equipped with Canal Defence Light Grant tanks. These were not used in battle. From 1947, it was in the 22nd Armoured Brigade under the 56th (London) Infantry Division