Liddell, not wishing himself "to be a slacker", joined the Officers' Special Reserve of the 3rd Battalion, Argyll and Sutherland Highlanders (Princess Louise's) of the British Army in 1912.

He spent 43 consecutive days in the trenches in command of the machine gun section and was awarded the Military Cross at Le Maisnil, France, before training as a pilot and joining No.

This caused momentary unconsciousness, but by great effort he recovered partial control of his machine when it had dropped nearly 3,000 feet and succeeded, although fired on, in completing the course and brought the plane back into the Allied lines.

[1] After having his leg removed and septic poisoning setting in, Liddell died of his wounds a month later at De Panne, Flanders, Belgium, on 31 August 1915, aged 27.

[6] On 29 August 2017 a memorial was unveiled outside the Discovery Museum in Newcastle upon Tyne, where Liddell and Privates Edward Lawson and Adam Wakenshaw are commemorated.