Oh well, if this is going to turn into a serious debate on BR traction policy in the 1950s and 1960s, FWIW I agree with
SikhWarrioR that BR ordered far too many types of diesel. It was a product of the chaos at the top of BR around the time of the modernisation plan, when the initial decision to stick with steam for the time being was ditched and they went for crash dieselisation, a daft move exacerbated by the fact that the regions had far too much autonomy, which the Western Region exploited to the full. All of the diesel-hydraulics were a waste of money - although the 52s and Warships were lovely machines, I grant - and we could sit here and rattle of a long list of other types that weren't worth the space they took up. It's fortunate that pretty much by chance BR ended up with a relatively small number of classes that happened to be excellent.
I wouldn't disagree with much of that, save to say that I am not sure it was "by chance" - more that the scattershot approach BR adopted did perhaps offer the possibility that
some of the classes might be accidentally quite good
When you think of the numerous failures, not to mention the now-respected locomotives that didn't always get a good start, the hit rate is pretty low: we seemed to hit problems with 2-stroke diesel pretty quickly (anyone remember the spectacularly unlovely Class 28s?), a lot of the early hydraulic stuff was problematic, then there were whole classes of locomotive that were doomed from the outset by being built to steam standards in steam locomotive works (I'm looking at you, North British).
It is in some ways testament to the designs that did work that we're still using 08s, 37s and 47s. I guess the 55s were always doomed once really fast MU traction appeared (hello HST), but there were all sorts of little locomotives (25,26,27,33) that quietly got on with things and did their job pretty well.
I think they probably nailed it when they commissioned the electrics, because the design brief was clearly pretty narrow, and we got the first of our "boring" locomotives - almost corporate (not that they'd have known what you meant by that then), simple boxes, one very much like another, with just some detail differences of technology to choose between them. Not nearly as interesting historically, though!
And that boringness is probably what makes the ones that didn't make it special. Peaks were too heavy, so they needed an extra axle, and we ended up with something really quite pretty as a result, and I guess they were probably a success story, too, but didn't seem to outlast the much less characterful 47s. Even some of the clunkers - those ugly, stunted 21s and 22s - had a certain 1950s austere charm about them.
*edit* If we're going to get
really heretical, the BR Standard steam engines shouldn't have been built either. The decision in the late 40s to stick with steam pending long-distant electrification and to ignore diesels was made in too much of a hurry, and the opportunity to introduce and thoroughly test a limited number of standard diesels slipped by whilst BR busied itself with building a series of engines that didn't really do much that lightly updated versions of existing types (which several of them were anyway) couldn't have done just as well. In other words, the traction fuck-up of the late 50s was a product of a hasty reversal of misconceived policies dating from right after nationalisation. That's my economic historian's head writing, though: my enthusiast's heart loves the Britannias and 9Fs.
I guess the steam problem was always going to be a tricky one. Diesels were a comparatively unproven technology at the point that the decision on steam was being made, and I guess, too, that the realisation that the incredibly labour-intensive railway was going to have to slim down a lot had not yet arrived, so steam still made sense. As it was, we weren't really ready for diesels when they did arrive, so they ended up being stabled and maintained on steam sheds, with all the implications for reliability and performance that brought.
But, from a purely aesthetic point of view, those Standard classes were a chance to demonstrate the epitome of steam development and engineering; and if we ever had to pick up again from where we left off on steam, they were a pretty good point to have reached
