At the outbreak of the war on 4 August 1914, Collet was based at RNAS Eastchurch. On 10 August he took part in the "Daily Mail"–sponsored "Circuit of Britain" race, which was not cancelled despite the declaration of war. He flew a German-built DFW Mars (No. 154), which the RNAS had bought in 1913, and refitted with a Beardmore 120 hp engine. Unfortunately mechanical problems forced him to make an emergency landing at Scarborough racecourse, where he was promptly arrested and questioned. After repairs were made, Collet completed the race, coming second.