Crocker was not to remain there long, however, as on 21 April 1940 he was promoted to the acting rank of brigadier and was appointed to command of the 3rd Armoured Brigade, in succession to Brigadier Vyvyan Pope, a fellow RTR officer. The brigade, alongside Brigadier Richard McCreery's 2nd Armoured Brigade and Brigadier Frederick Morgan's 1st Support Group, formed part of Major-General Roger Evans's 1st Armoured Division (formerly the Mobile Division), then serving in England but preparing to move to France. Crocker's brigade was depleted as the British Expeditionary Force (BEF) was expelled from the continent during the Battle of France in May–June 1940. Landed at Cherbourg as the rest of the BEF retreated to Dunkirk in late May, the division unsuccessfully attacked the German bridgeheads over the River Somme before returning to Cherbourg where the remnants (including the brigade's last 13 tanks) were evacuated. Crocker and his brigade were evacuated in mid-June, Crocker himself returning with Lieutenant-General James Marshall-Cornwall on the last ship.