Railways are wonderful, railways are interesting, railways are super-dooper-woo-wooo-hey. It is a little-known fact that the Class 87s have, on occasion, been as far south as Reading, and frequently...

[Note: 672 pages of mind-numbingly dull drivel omitted]

...whereas, however, the Bulleid "Merchant Navy" Class, did, of course, later have their chain-driven valve gear replaced with more conventional equipment for reasons of maintenance.

So there you have it - railways really are interesting.