The A4 class of the London and North Eastern Railway
I said above that Flying Scotsman must be the most famous steam locomotive of all, but Mallard would give her a run for her money. There is something about the shape of the A4s that set them apart. Even though they were not the shape of things to come (as thought in the 1930s), they somehow blended the aesthetics of classic steam locomotive design with a futuristic look. I remember owning a Dinky Toy Silver Link loco and carriages, and it always had pride of place amongst the other Dink Toys that I had.
Gresley A4 Pacifics
4498 Sir Nigel Gresley
Originally numbered 4498 by LNER, this loco was renumbered to 60007 in BR days.
60009 Union of South Africa
60019 Bittern
60022 Mallard