Baker Street track layout.

I believe that the loco from the loco loop was used. I'm almost sure that it's been published. Maybe the Howson books or that neat little softback publication on the Met locos.
I cannot check at the moment but I think that the coal train arrived and pulled into Plat 1 then the loco from the loop did the shunting and took the train away. The incoming loco then went to the loco loop.