Walmsley's flying training was deferred for a time but in due course he was sent to
Rhodesia, where he gained his
wings. He returned to England in June 1942 for the final stages of his training at
No. 61 Operational Training Unit (OTU). Holding the rank of
sergeant pilot, he was posted to
No. 611 Squadron three months later. Based at
Biggin Hill, this unit operated the
Supermarine Spitfire Mk. IX fighter on offensive operations to German-occupied Europe.
Commissioned as a
pilot officer on 4 January 1943, Walmsley made his first claim for an aerial victory five days later; this was for a
Focke Wulf Fw 190 fighter probably destroyed near
Abbeville.
Operations over France On 17 January, also near Abbeville, Walmsley damaged a
Focke-Wulf Fw 189 observation aircraft. A Fw 190 was damaged by Walmsley near
Dungeness on 9 April, and he repeated the feat on 16 May, damaging a Fw 190 near
Morlaix. Promoted to
flying officer at the start of July, he destroyed a
Messerschmitt Bf 109 fighter to the west of
Amsterdam on 25 July. The same month, No. 611 Squadron moved to
Matlaske where it began converting to the Spitfire Mk. LF. Vb fighter in preparation for low-level operations. In August Walmsley was posted to
No. 132 Squadron to become one of its
flight commanders. His new unit was commanded by
Squadron Leader F. Colleredo-Mansfeld, Walmsley's former flight commander at No. 611 Squadron. Tasked with carrying out offensive sweeps and escort missions to France with its Spitfires, the intensity of operations increased as the year progressed. Walmsley damaged a Fw 190 near
Courtrai on 21 December. In the New Year, on 7 January, he shot down a Fw 190 to the east of Abbeville. He was taken off operations for a rest in April and was awarded the
Distinguished Flying Cross (DFC). After attending the
Central Gunnery School, Walmsley carried out instructing duties with No. 57 OTU at
Eshott from May to October. He was then posted to
No. 130 Squadron as a flight commander. Based at the
Deurne airfield in Belgium, this was on ground attack duties, carrying out sorties with its Spitfire Mk. XIVs to support the Allied ground forces as they advanced into France and Belgium. Poor weather inhibited the squadron's operations supporting the Allied advance into Germany until spring, at which time aerial engagements with
Luftwaffe fighters became more frequent. Walmsley, who was for a time acting commander of the squadron, shot down a Fw 190 near
Hamm on 13 March, and this was followed two weeks later by the destruction of another Fw 190, one of four intercepted by his section, to the south of
Warendorf. A
Junkers Ju 52 transport aircraft was shot down by Walmsley on 13 April over Vechlin and a week later he caught and destroyed two
Fieseler Fi 156 Storch light aircraft on an airfield at Vechlin. he shot down a Fw 190 near
Oranienburg on 20 April. On 23 April Walmsley shot down a pair of
Messerschmitt Bf 108 trainer aircraft over
Parchim airfield. Later that day he was appointed commander of
No. 350 Squadron. Based at
Celle, this was a unit which was composed largely of Belgian pilots which had evaded the German occupation of their country. At the time Walmsley became commanding officer, it was flying Spitfires in the aerial fighting around
Berlin. The day after taking command, he destroyed a Fw 190 at Klienen airfield. This was followed on 25 April by his shooting down of another Fw 190 near
Rechlin. His final aerial victory was a share in the destruction of a Fw 190 near Plaver Lake on 26 April. By the time the war ended in Europe, the squadron was based at
Fassberg in Germany. His successes were recognised with an award of a
Bar to his DFC. The published citation read: ==Postwar service==