As the advance moved forward to Benghazi, Whistler was transferred to command the 131st Lorried Infantry Brigade on 19 December 1942. This brigade (composed of three TA battalions, the 1/5th, 1/6th and 1/7th, of the Queen's Royal Regiment (West Surrey) and often referred to as "The Queen's Brigade") had originally arrived in Egypt as part of the 44th Division but by this time was the mobile infantry element of the 7th Armoured Division, the famous "Desert Rats", after the 44th Division was broken up. The 7th Armoured Division, which also comprised the 22nd Armoured Brigade under Brigadier Philip "Pip" Roberts and supporting units, was then commanded by Major-General John Harding. Whistler led the 131st Brigade, which, because of its role with armour, was often in the forefront of events, through the rest of the fighting in North Africa until the surrender of the Axis forces in Tunisia in May 1943. Whistler led his troops through the Battle of El Agheila in December 1942, the capture of Tripoli in mid-January 1943, where the division's GOC, Major-General Harding, was severely injured by shellfire and replaced by Major-General George "Bobby" Erskine, and along the coastal strip, capturing Msallata, Zuwara, Zaltan and Pisida. The brigade then took part in the Battle of Medenine on 6 March 1943 and the Battle of the Mareth Line at the end of March. Whistler's frequent visits to the front line earned him the nickname of "Private Bolo".