I don't normally do posts on British railway locomotives for a couple of reasons, first the British do railfan far better than I ever will and second, there is just so many odd-looking (to my North American eye) steam locomotives, I can't keep track of them.
But the Crampton might be one of the oddest of all, this high speed passenger locomotive has a single driver and it's located behind the firebox in order to get a 7 1/2 foot diameter wheel while maintaining a low center of gravity. The large diameter driver keeps the wheel revolutions down to minimize the balancing issues of reciprocating/ rotating weights.
I would think poor weight distribution would have robbed this machine of much of its tractive effort.
The concept must have worked well enough as it led to a series of even larger diameter single driver locomotives of more conventional design that lasted well into the twentieth century in various European countries.
There is an American connection, the president of the Camden and Amboy Railroad of New Jersey was impressed enough with the Crampton to want them for his line. Previous post here. Oddness carried to a new level.