The Discworld is very much like our own - if our own were to consist of a flat planet balanced on the back of four elephants which stand on the back of a giant turtle, that is . . .

Change is in the air for Moist von Lipwig, swindler, con-man, and (naturally) head of the Royal Bank and Post Office.

A steaming, clanging new invention - a steam locomotive named Iron Girder, to be precise - is drawing astonished crowds. Suddenly it's a matter of national importance that the trains run on time.

Moist does not enjoy hard work. His input at the bank and post office consists mainly of words, which are not that heavy. Or greasy. And it certainly doesn't involve rickety bridges, runaway cheeses or a fat controller with knuckledusters.

What Moist does enjoy is being alive, which may not be a perk of running the new railway. Because, of course, some people have OBJECTIONS, and they'll go to extremes to stop locomotion in its tracks.