2020.03.11 Cambrian extra trains
Our starting point is the Working Timetable (WTT), covering both passenger and goods traffic in an area, and in the fifties generally issued in Summer (May to September) and Winter versions. This would contain all trains that ran regularly, usually recorded separately for Sundays, as fewer trains ran, and with trains that ran only on some days indicated by markings such as SO and SX, and sometimes rather more complicated ones such as the MWFO and TThSO for the alternate stopping patterns of the Oswestry to Newtown pickup goods.
That gives a good start, but in some cases, particularly in mining areas, there was an additional set of trains of which details were published only locally, usually on a weekly basis, and it is very difficult by now to find any trace of these. Fortunately we can sometimes find people who can remember what used to happen, although this gets harder as time goes on.
In addition to patterns of extras, there would have been many cases of additional trains that did not follow any pattern. Some examples would be troop trains, school excursions, holiday trains, trains to sporting fixtures, excursions to special events, and diversions due to track work - as well of course as all the additional trains directly associated with track work. All these would be shown on Special Train Notices (STN) which would be published weekly. Occasionally we come across these, but few have survived.