On 15 October 1941 Crocker, by now having commanded the 6th Armoured Division for just over a year, handed over command to Major-General Herbert Lumsden upon being selected to command the 2nd Armoured Group in Home Forces. His rank of Major-General was made temporary on 22 October 1941. He was not to remain there long, as on 16 March 1942 Crocker was promoted to the acting rank of Lieutenant-General and was given command of XI Corps, taking over from Lieutenant-General Noel Irwin, who was being posted to IV Corps in the Mediterranean and Middle East theatre of World War II. Aged just forty-six, this made Crocker one of the youngest corps commanders in the British Army. It is quite probable that Alan Brooke, who still thought highly of Crocker and was now Chief of the Imperial General Staff (CIGS), secured for him his new appointment. Crocker's new command, which had Harold Morgan's 45th, Evelyn Barker's 54th (East Anglian) and Eric Miles's 56th (London) Infantry Divisions, along with the 21st Army Tank Brigade, under command, was based in East Anglia, where it had responsibility for its defence in the event of an invasion, and was serving under Eastern Command.