The consequences of a hold can be quite a chain reaction if things go wrong in the right way...
In the late 1980s, it was still generally possible for anyone to request a reasonable hold if they had tight connections - and it is probably no coincidence that this was abolished not long after a particularly spectacular and incompetent screw up.
An evening passenger from Farnham one Saturday noted that there was a possible double connection, but that each was particularly tight and that missing either would add about half an hour to the journey, which was to an intermediate station between Raynes Park and Epsom. Faced with this potential hour of delay, a request was made at Farnham that the connections at both Surbiton and Raynes Park should be guaranteed, and this was agreed.
Upon approaching Surbiton, the train ground to a halt and the passenger, looking out, could see a red signal ahead and that another train was occupying the up fast platform. Five minutes later, no slow train had come past and the other train was still blocking the platform ahead. Then there was an announcement about a points failure at Surbiton, and realisation slowly dawned that the train ahead was the one that was supposed to be in the up slow platform and was being held...
The passenger then went along the train to find the guard and explained why the train in front was not moving - the guard then contacted the driver, who was then seen climbing down and using the signal post telephone, a couple of minutes later the train in front moved off and the passenger was finally on the platform, now some 20 minutes late, waiting for the next stopping service.
This the passenger duly boarded and after switching back to the up slow it deposited him at Raynes Park, expecting to have another long wait.
It then became obvious that all the down slow services were late as well. Apparently nothing had come through for about half an hour.
What transpired was that British Rail had indeed held the second connection as well... but at Wimbledon, not Raynes Park. Nobody had thought to release it either after the earlier error at Surbiton ( of holding a service for the one stuck behind it ) had become apparent, nor to check what exactly was going on - which should have been done within minutes.
When a hold instruction goes wrong, it can go really very wrong.
This was in the days when the Farnham and Basingstoke services still split and joined at Woking, so not only did they now have a whole half hour segment of the suburban services running with delays of between 5 and 40 minutes, they also had a late running batch of inbound fast line services with delays of 5 to 25 minutes, one of which - with the heavier end of the delays - would need to split when going back out to serve two different destinations and then rejoin to different inbound units on their way back again. The entire South West Division timetable would have been disrupted to some extent for the rest of that evening.