He was 23 years old, and a sergeant in the 5th Machine Gun Company, 5th Brigade, 2nd Division when the following deed took place for which he was awarded the VC.
On the night of the 28/29 July 1916 near Pozières, France, during a night attack the infantry was temporarily driven back by the intense machine-gun fire from the enemy trenches. Many wounded were left in "No Man's Land" lying in shell holes. Sergeant Castleton went out twice in the face of this intense fire, and each time brought in a wounded man on his back. He went out a third time and was bringing in another wounded man when he was himself hit in the back and killed instantly.
Castleton is buried at Pozières British Military Cemetery, Somme, France, 3 miles NE of Albert (Plot IV, Row L, Grave 43).