Single engine fast jets
There have been plenty of single engine fast jets with more than adequate performance, but the UK has certainly tended to go for twins, since the Hunter
Mirage III & 2000
Etendard
Corsair
Crusader
Viggen
Draken
Skyhawk
F104
F102 & F106
G91
F16
Gripen
etc...
Curious that fast jet trainers (apart from AlphaJet) all seem to be singles. Maybe they follow Lindbergh's logic that two engines just doubles the probability of an engine failure....