In December 1914 , aged 18 , Gilmour left school and joined the Argyll and Sutherland Highlanders regiment with the rank of second lieutenant .
He was also a member of Officers ' Training Corps , with the rank of sergeant .
In December 1914 , aged 18 , member left school and joined the Argyll and Sutherland Highlanders regiment with the rank of second lieutenant .
He was also a member of Officers ' Training Corps , with the rank of sergeant .