Following the outbreak of the First World War, he joined the New Zealand Military Forces and served with the Army Service Corps during the Gallipoli Campaign and on the Western Front in a field bakery.

On 30 September 1918, during the Hundred Days Offensive, as well as carrying messages while under gunfire, he deactivated demolition charges set by German forces to destroy a bridge.

[2] Crichton was now serving with the 1st Field Bakery,[2] which was part of the NZASC Divisional Train supplying the New Zealand Division.

[2] On 30 September 1918, during the Hundred Days Offensive, Crichton's platoon was trying to force a crossing of the Scheldt River, near Crèvecœur, when it came under machine-gun fire.

[1] Fully clothed, Crichton swam the river and despite being exposed to German gunfire as he made his way up the bank, he was able to make his report to the company's commander.

While waiting assistance from other units, Crichton decided to deal with the demolition charges on the bridges and took out the fuses and detonators.

[10] The citation for his VC read: For most conspicuous bravery and devotion to duty when, although wounded in the foot, he continued with the advancing troops despite difficult canal and river obstacles.

Later he undertook on his own initiative to save a bridge which had been mined, and, though under close fire of machine-guns and snipers, he succeeded in removing the charges, returning with the fuses and detonators.

Though suffering from a painful wound he displayed the highest degree of valour and devotion to duty.Crichton's VC was the last to be earned by a serviceman of the NZEF during the First World War.

[12] Together with three other New Zealanders who had been awarded the VC,[Note 1] he received his medal from King George V in an investiture at Buckingham Palace on 27 February 1919.

[15] Crichton was part of the New Zealand contingent sent to London in 1937 for the coronation of King George VI and Queen Elizabeth.

[16] During the Second World War, Crichton served in the Home Guard and worked on merchant ships travelling between New Zealand and England.

[17] Several memorials are dedicated to Crichton, including a plaque on the first house in which his family lived in Carrickfergus, his place of birth, in Northern Ireland.

His name is recorded on the Armadale & District Roll of Honour, which included the Scottish village of Blackridge, where he had lived as a boy.