Second World War
He joined the Welsh Guards at the outbreak of the Second World War in 1939, and was trained at Sandhurst. In February 1940, before his officer training was complete, Mather volunteered to join the 5th Special Reserve Battalion, Scots Guards.
The battalion was formed in anticipation of supporting Finland in the Winter War in 1939–1940, but the conflict ended before it left the UK. Mather returned to training with the Welsh Guards and was commissioned in March 1940. He volunteered for training at the Irregular Warfare Training Centre in Lochailort in October 1940, joined No. 8 Commando, and headed with the unit to North Africa in January 1941 as part of Layforce.
After 8 Commando was disbanded on 1 August 1941, Mather joined "L Detachment", the nucleus of the future SAS headed by David Stirling, where he joined raids on Axis airfields, notably the raid on Sidi Haneish airfield in June 1942.
In October 1942, he was offered the opportunity to join his elder brother on the staff of General Montgomery. Montgomery was a family friend, through his wife, Betty. Rejoining Stirling's force for a last operation deep behind enemy lines, he was captured by the Italians in Tripolitania on 20 December 1942.
He was transferred to Italy by submarine, and spent 9 months as a prisoner of war in Fontanellato in Northern Italy. He escaped in September 1943, shortly after the Italians agreed an armistice with the Allies, and walked 600 miles down the Apennines to the Allied lines near Campobasso, north-east of Naples.
He returned to England in November 1943, and rejoined Montgomery as a liaison officer in early 1944 to assist with preparations for D-Day. He landed on D+1, and remained with Montgomery through the operations in Northern France and Belgium, acting as Montgomery's eyes and ears on the front line.
He was awarded the MC for a successful reconnaissance mission in Nijmegen on 18 September 1944, on the second day of Operation Market Garden, while it was still occupied by the German Army. On 9 January 1945, he survived being on an Auster that was shot down near Grave in the Netherlands: the pilot was killed, and another passenger, Major Richard Harden, took the controls and crash-landed while Mather deployed the flaps. Mather was hit by four bullets and badly injured, suffering 13 separate wounds and losing a kidney. He spent several months in hospital before rejoining Montgomery in July 1945 near Osnabrück.
