The Steam Railmotor in Cornwall 

It has a very compact vertical boiler, which is fixed to the rotating power bogie. Coal bunker is at the front of the boiler end, with a water tank slung between the frames (the massive box thing if you look under the loco). Other than that works like a normal steam engine, though with 2 sets of controls, 1 for each end. There are a number of videos and images online that show the cab. Interesting, you cannot fire the loco while it is in motion as it will cause blowback (or so I‘ve been told).