In 1914, he became a temporary Chaplain to the Forces, serving until 1919 and winning the Military Cross.

He was appointed as a temporary Chaplain to the Forces (South African Overseas Brigade), in 1917, was again wounded, and was awarded the Military Cross for gallantry in 1918.

He was a temporary Chaplain to the Forces from 1944 to 1946.

During the Great War, he was a temporary Chaplain to the Forces.

In addition, between 1915 to 1918 he was a temporary Chaplain to the Forces.

Mayne was commissioned as a temporary Chaplain to the Forces, 4th class, Army Chaplains Department on 30 October 1914.

He was promoted temporary Chaplain to the Forces, 3rd class, on 23 November 1916, and was posted as Senior Chaplain to the Forces to the 33rd Division.

After a curacy at Portsea he was a World War I temporary Chaplain to the Forces.

He was then a temporary Chaplain to the Forces.

By October 1943, he was Chaplain to the Forces (2nd Class), and temporary Chaplain to the Forces (1st Class).