There was only the one. Gresley's experimental high pressure 4 cyl. water tube boiler of marine design. It was rebuilt in 1937 with an ordinary boiler but with streamline cladding similar to an A4. I saw it at York several times and it was always known as the "Unamed streak". The end came after a derailment, near Peterborough, if my memory serves me correct, and was withdrawn.
':D'':D'
Oh! and of course, not forgetting, UKTrainSim ':)'
Blue Arrow
TrainSim.com
Making Tracks
Facingpoint
3D Trains
3D Trainstuff
Aerosoft
Contact Sales
Pro Trains
and probably many more! ':)'':)'':)'':)'