F/Lt. I. L. McG. Hallum was born on 2nd November 1918 in Edinburgh.
He was educated at Repton School and learnt to fly at the Phillips and Powis Aircraft Ltd. Training School under the auspices of the Royal Air Force. He first flew solo on 5th April 1937 in a Hawk Trainer.
After his training, Ian was posted to 2 Squadron based at Hawkinge.
On 3rd September 1939, War was declared on Germany and 2 Squadron was posted to Abbeville/Senon/Labiusuere region in Northern France on 6th September. Whilst in Abbeville, Ian carried out frequent reconnaissance flights over the field of battle until 19th May 1940, when the Squadron was sent back to Britain due to the Germans' advance.

In July 1940, Ian was sent to the Photographic Reconnaissance Unit (PRU) at Heston in Middlesex for training. In August 1940, he was then posted to 225 (A.C.) Squadron at Tilshead in Wiltshire. There he was trained in the flying of Fighter aircraft, particularly the Spitfire.
On 27th September, Ian was posted to 73 Squadron at Castle Camps in Suffolk. He was only at Castle Camps for a short time culminating in a crash landing on 3rd November 1940 near Redhill, due to poor visibility.
At the beginning of October 1940, Ian was posted to 222 Squadron based at Hornchurch in Essex. He was one of the few experienced pilots available to supplement the exhausted Battle of Britain Pilots. During this period with 222 Squadron, he flew up to four sorties a day. On 17th October, Ian claimed damaging an M.E. 109 and between 2nd and 25th October he claimed 1 M.E. 109 destroyed, 2 damaged and 1 probable.

After several postings in the UK he was posted to 21 Air School of the South African Air force based in Kimberley, and then onto 20 S.F.T.S. Royal Air Force at Cranbourne in Southern Rhodesia. He remained with this unit until June 1942. At the end of this posting he was promoted to Squadron Leader and returned to active flying as a photo - reconnaissance pilot.

Ian was flying unarmed Hurricanes on Tactical Photo- Reconnaissance missions and on 24th August 1942 he failed to return from his mission over the El Alamein battlefield. On 26th September 1942, the Germans broadcast his name as having been captured and he was now a Prisoner of War.

On or about 11th February 1945, the prisoners met up with some Americans and were freed from their captivity. From April 1945 until October 1945, Ian was on repatriation leave.
Following further courses, Ian was appointed to the position of Officer Commanding the Aberdeen University Air Squadron. On 10th May 1952, whilst flying a training flight in a Chipmunk with Cadet officer John Lawrie, the aircraft they were in crashed, killing bith men.