"On 8 October 1939, over Jutland, a Lockheed Hudson became the first RAF aircraft to shoot down a German aircraft"
so far for the RAF
and in total
" 8 September 1939, Hawk 75 from Groupe de Chasse II/4 were credited with shooting down two Luftwaffe Messerschmitt Bf 109Es, the first Allied air victory of World War II on the Western front."
the Martlet was "just" the first US build FIGHTER in UK service that shoot down an enemy...and that was december 1940