Walter Allason was born in Paddington in London in 1875, the son of Elizabeth Thomazine née Allen and Alfred Allason, a retired officer of the Royal Marines. He was the grandson of the architect Thomas Allason. The 1891 Census records Walter Allason as a scholar at Bourne Hill School and reading for the Army Exam. He passed out of the Royal Military College at Sandhurst as a Gentleman Cadet, following which he was commissioned as Second Lieutenant in the 4th Manchester Regiment on 23 July 1894, and was promoted to Lieutenant in 1896. He was transferred to the Bedfordshire Regiment as a Second Lieutenant on 9 December 1896 and was promoted back to Lieutenant on 1 July 1898. After service in the Second Boer War, Allason was seconded for service in the Foreign Office in 1902. He was promoted to Major in October 1913 and was appointed second in command of the 1st Battalion when they were posted to France on 16 August 1914, at the start of World War I. He was wounded in action and in 1915 was awarded his first Distinguished Service Order. He was wounded again on Hill 60 in April 1915 and after his recovery he was appointed to command the 8th Bedfordshire Regiment, but rejoined the 1st Battalion for the Battle of the Somme in 1916. He was awarded a Bar to his DSO for the Somme, possibly as a result of the Battalion's attack on Falfemont Farm in September 1916. The citation for the Bar reads:
Maj. Walter Allason,D.S.O., Bedf. R. For conspicuous gallantry in action. He executed an attack with the greatest initiative and resource, thereby enabling a strong enemy position to be captured. He handled his battalion with great skill throughout the operations.
Allason was wounded for a third time in December 1916 when, inspecting the trenches at the front line he was accidentally shot by a young and jumpy Subaltern. The wound was serious enough for Allason to be removed from duty, only able to return to the command of the 1st Battalion after the war. In 1918 Allason was promoted to GOC 52nd Brigade17th Division. Allason was promoted to Brigadier General and placed on the retired list on 25 October 1925 when he reached 50 years of age, the compulsory retirement age for officers.
In 1896, 1897, 1902, 1908, 1909 and 1922 Walter Allason won the English Plunging Championship and the Aldershot Command Officers' Challenge Cup in 1912. In 1924 as a Lieutenant-Colonel he won a first place medal in the Plunging category in the Inter Unit Team Swimming Competition at Aldershot Command.
After retirement
In 1939, listed as a widower, he was living at Brackley in Northamptonshire with his daughter. At that time he was the Area Chief Warden in the Air Raid Precautions while his daughter was attached to a Voluntary Aid Detachment in a Mobile Unit. His book Military Mapping and Reports was published in 1940 by Duckworth Books and went through six editions by the time of his death. Brigadier General Walter Allason died in London in January 1960, aged 84.