At the outbreak of World War I, Alcock joined the Royal Naval Air Service as a warrant-officer instructor at the Royal Naval Flying School at Eastchurch in Kent. It was whilst at Eastchurch that Alcock received his commission as a flight sub-lieutenant in December 1915. In 1916 he was transferred to a squadron operating at Moudros, on the Greek island of Lemnos. While stationed at Moudros he conceived and built the Alcock Scout, a fighter aircraft built out of the remnants of unused and abandoned aircraft.
On 30 September 1917, whilst piloting a Sopwith Camel Alcock attacked three enemy aircraft, forcing two to crash into the sea. For this action he was awarded the Distinguished Service Cross. After returning to base he then piloted a Handley Page bomber on a raid to Constantinople. He was forced to turn back to base after an engine failed near Gallipoli. After flying on a single engine for more than 60 miles, that engine failed and the aircraft ditched in the sea, near Suvla Bay. Alcock and his crew of two were unable to attract nearby British destroyers, and when the plane finally began to sink they swam for an hour to reach the enemy-held shore. All three were taken prisoner next day by the Turkish forces. Alcock remained a prisoner of war until the Armistice and retired from the Royal Air Force in March 1919.

On 18 December 1919, Alcock was piloting a new Vickers amphibious aircraft, the Vickers Viking, to the first post-war aeronautical exhibition in Paris when he crashed in fog at Cotteacute;vrard, near Rouen in Normandy. Alcock suffered a fractured skull and never regained consciousness after being transferred to a hospital in Rouen. He succumbed to his injuries the following day.
His grave in Southern Cemetery, Manchester is marked by a large stone memorial
Source : Wikipedia