Well, these were just my thoughts as they came to me. I forgot to mention the huge number of sheds in the Lancashire and Yorkshire areas (although Springs Branch has spoken up for his own MPD). I really didn't get to those areas until the later part of the 60s, so it's difficult to gauge how big they were say, c 1960. Again, there were 'glory' depots like Edge Hill, Longsight and Holbeck (I say glory because they were the A shed and had an allocation of named, express passenger locos), but I have no idea how large the 'less glamorous' ones were, say, Warrington Dallam or Wakefield (even though I did 'do' the latter in 1965 on a shed bashing weekend - but it was all something of a WD-filled blur).
One shed which struck me as huge when I actually went there was Oxley (GWR, Wolverhampton). I did it in 1965, well into diesel days, but I remember marvelling at what I might have seen five years earlier.
But nothing could have prepared me for March in, I think, Easter or Summer 1961. This tiny little town, which even today (almost) nobody knows west of Peterborough, south of Cambridge or north of Spalding, seemed to have locomotives spread over a vast area of about one square mile. Diesels had taken most of the GE workings when I was there, but there were still (as I recall) old GE J15 and J17 0-6-0s dumped in lines, B1s in steam and there seemed to be a surfeit of Britannias chugging around with little to do, having been displaced (I presumed later) off the Norwich expresses and not yet transferred to the LM. There were also - I don't know - perhaps 30-40 'foreign' steam, presumably having worked in from the GN and LMR. It was truly awe inspiring to me as a nine- or perhaps 10-year old.
Stratford is interesting because, as far as I can tell, it was an 'all-in-one' facility. That is to say, many of the lines out of London had two sheds, eg Kings X and Hornsey, Camden and Willesden, Kentish Town and Cricklewood. From what I gather, when in their prime, the former of the pair was the passenger shed, the latter had mainly freight diagrams. I presume this was due to a more or less accident of history, ie (say) the London and Birmingham opened Camden, close to the terminus, first, but as traffic grew, needed another depot. Because of land shortage/prices (and possibly being closer to goods yards), the second depot was built further from the terminus and 'relegated' to freight duties.
But the GE combined both functions, and a works, at Stratford. (Similarly, minus the works - Old Oak on the GWR.) BICBW - I'm sure someone will be along soon to correct me on any misuderstandings I have here!
I feel this analysis only really works for London. I've never worked out the difference in roles between eg Heaton and Gateshead, Haymarket and St Margarets, or the mass of Glasgow sheds (Dalry Road, anyone?).
