A thought I just had.
I'm surprised the Mikado (2-8-2) arrangement never gained traction in the UK. On a shallow level of understanding, the UK's operating situation is remarkably similar to Japan's. Japan ended up almost exclusively using Mikados after the first were delivered from the US.
I know Gresley had his P1 & P2, & there was the GWR tank. Still, the 2-8-2 saw some good service elsewhere as a passenger loco.
I couldn't see the GWR ever committing to any number of Mikados - too entrenched in their ways. Would Stanier or Riddles have attempted the type? Or maybe Bulleid?