 After hearing of the success , Watt called the team and asked if they would be available for testing in September , when a combined fleet of Royal Navy ships and RAF Coastal Command aircraft would be carrying out military exercises in the Channel . On the afternoon of 3 September the aircraft successfully detected the battleship HMS Rodney , the aircraft carrier HMS Courageous and the light cruiser HMS Southampton , receiving very strong returns . The next day they took off at dawn and , in almost complete overcast , found Courageous and Southampton at a distance of 5 to 6 miles ( 8 @.@ 0 – 9 @.@ 7 km ) . As they approached the ships and eventually became visible , they could see the Courageous launching aircraft to intercept them . The promise of the system was not lost on observers ; Albert Percival Rowe of the Tizard Committee commented that " This , had they known , was the writing on the wall for the German Submarine Service . " 
