So there I was, on the cusp of teen age, with about as mixed up a train set as a boy could have. The only commonality was gauge (OO of course, in those days).
As to location, it was doubtless set on an island somewhere north of France, but that was as far as it went, with a possible leaning towards the west of that particular island.
As to era, that was clearly 1^st January 1923 to 1^st January 1970, the well-known Big Four Rail Blue Epoch.

The lads from school and I had finally succumbed to train-spotting, or rather HAP-spotting, and occasional EPB-spotting. Indeed, if we played our cards right at Strood we might spot the ‘Marinex Gravel’, a Class 33 hauling hopper wagons full of sea-dredged gravel, passing through at about 5pm.

Evidence - I had run out of HAPs!

Eventually the 2-HAP units no longer quenched the thirst for numbers, and so the concept of ‘Expedition Awaydays’ was introduced, to initial parental trepidation. This involved several boys leaping on a train for London, and hitting every station on the Circle Line, and one or two outside it.

Essentially it went like this:-
Leap on train at Maidstone East or Rochester and arrive at Victoria having had head out of train window for the entire journey. Clean eyes. Take all numbers at Victoria, and hasten to Paddington. Now Paddington was exciting! The Westerns were still noisily in command, backed up mostly by Class 47’s. We took an excursion from Paddington to Acton Main Line to see the Westerns at speed, roaring through the station. I still have a photo, but there is so much camera shake from the excitement that it’s barely recognisable, no way am I going to show it here. Well OK, just this once, taken with my Instamatic 33.

By this time the Westerns were getting so filthy that even sophisticated photographers were affected. This was 1974 I think.

Back to Paddington and we would try Marylebone, invariably disappointing with a DMU or two, we cut it (and Broad Steet) out of later Expeditions. Next came the big three, Euston, St Pancras and Kings Cross. We probably favoured the former due to the AC Electrics dominating most trains, Classes 81 to 86 (the Class 87 was about to appear) with the occasional Class 40, and happy hours were spent loitering on our favourite platform. Our second excursion was always to Willesden Junction to see some electrics at speed, there was something exotic about the AC electrics.

St Pancras was the cavernous affair it still is, and much darker, though not terribly busy. It was here that we would eat our British Rail cheese sandwiches and drink our British Rail tea on an item of British Rail Universal Trolley Equipment (BRUTE), at the end of the platform. I recall Brutes being everywhere... suspect there are not enough on models of the era. Not many restaurants could boast a view like a Brute! Peak Classes 44, 45, 46 ruling the roost. I had a soft spot for these huge beasts, they looked so good! Kings Cross was Deltic heaven, usually supported by Class 31 and 47.

We invariably visited Liverpool Street and initially the very run-down Broad Street. Liverpool Street provided a few locomotives, Class 40, 31 and 47 in the main, long before the AC electrics gained a toe-hold.

We normally skipped Fenchurch Street, Cannon Street, London Bridge and Blackfriars/Holborn Viaduct. Time was tight, and our last flourish of the day would be an hour on the end of Waterloo, followed by an hour at Clapham Junction, during the rush hour. We would get more numbers here than during the rest of the day put together, often the numbers would appear faster than we could record them. Admittedly they were EMU numbers, CEPs and VEPs and BIGs and SUBs etc, but they all counted.
And so we’d head for home, with a heavy haul of numbers.

And everything we saw and spotted was rail blue, on every one of these expeditions.

We did about 5 of these Awayday Expeditions, but times were changing, and a new phenomenon was beginning to appear on the horizon. Girls. A lot more difficult to collect than train numbers, I soon realised. The trappings of teenage were beginning to encroach.

Last night I laid them all out on the carpet, and after gloating for a moment, I realised how many I had collected over the years, without really trying, may have missed a couple too. Obviously some are historical facsimiles, I'm not that old.