From an article by Robert Hoskins, Celtic Football Club and the Great War

"One of those players [two Celtic players who died at The Somme] was the enigmatic Welsh International goalkeeper Leigh Roose who also held a Doctorate in Bacteriology, who played on loan to Celtic once in March 1910. Leigh joined the 9th Royal Fusiliers in 1914 and rose to the rank of Lance Corporal and won the Military Medal. Leigh died on 7th of October 1916, his Battalion was caught up in fierce fighting in the Battle for Montauban. At 1:45pm Leigh's regiment led the attack on enemy lines, encountering heavy machine gun fire on the way. On reaching the top of the nearby ridge, the attacking battalions were practically decimated by heavy shelling and machine gun fire. Like many attacking manoeuvres throughout the 1st World War, the objectives of this attack were never reached. That one day's attack highlighted the human tragedy that was the First World War, costing the lives of 25 men with an additional 165 missing presumed dead and 132 wounded for no material gain. As one of those 165 who is still 'missing' Leigh's name is inscribed on the massive Thiepval Memorial to his 72,000 other comrades who died in the Battle who also have no known grave."