Captain McGregor of No. 1 Company, 15th Battalion (48th Highlanders) was killed by the first Chlorine attack of the war while defending the trenches with his company. When the day was over, there remained in the battalion 3 officers out of 27 and 316 Other Ranks out of 953. The rest were killed, wounded, missing in action or captured.

In 1921, and following the resumption of regimental shooting, the McGregor Club was formed, composed of marksmen, to perpetuate his memory as McGregor had been an avid marksman.