Allendale Coulson was the son of the Reverend John Coulson, vicar of Holy Trinity, South Shields, and his wife, Kate Emily. His younger brother, Reginald Thomas also went to the High School.

His father died when Allendale was 14.

On leaving school Allendale joined the Jarrow branch of Barclays Bank.

During the war he served with the 4th Northumberland Howitzer Brigade of the Royal Field Artillery, as Lieutenant, and later as temporary Captain.

He was reported missing on 9-May-1915. and the High School's records show that he was taken prisoner on 12-May-1915, when he was taken to Halle prisoner-of-war camp, set up in a disused factory about 20km north-west of Leipzig.

He remained a prisoner-of-war until after the Armistice, and was repatriated on 18-Nov-1918.

Little is known about the rest of his life, but he died towards the end of 1970 in Basingstoke.