Funny enough similar things happen on the South Western Railway. The other day the 8.02 Woking to Waterloo was delayed due to a train fault. The inbound ECS arrived 8.05. The 8.05 Woking to Waterloo left first at 8.06¾. Now when on time that has to wait at West Byfleet for 7 minutes to enable a more even pattern of trains for stations north of that to Surbtion. However this then meant the 8.02 was stuck outside the station awaiting a platform, as that one never waits at West Byfleet. There are no other stations between Woking and West Byfleet that it can wait at, so it must have waited in between stations. The 8.02 left at 8.09, as it had to wait for the 8.06 fast to leave platform 2, that leaving a minute late.
After then getting further delayed further up the line, by the 8. 42 at Surbiton, it was now 21 minutes late. It only left Woking 7 minutes late.
Had the 8.02 been able to depart first, it wouldn't have been delayed by as much. I suspect the 8.05 could have made up its lost time at West Byfleet.
Something similar happened today. Due to a signalling issue, the 8.02 arrived in a 8.05. However although they were announcing delayed trains, no one was bothering about the 8.02. It kept being due in a minute later on the board until it final said delayed. At which point one or two people ran/faat walked to catch the 8.05. As I got to platform 1, shortly before 8.05, I could see the service that forms the 8.02, arriving into the station.
The 8.05 left a minute late, with me on it. Now the 8.02 will be stuck behind us for at least 7 minutes and may well be another 21 minutes late leaving Surbtion. Alas I didn't know about the signalling problems or I'd have taken a different route to my destination, my destination being a station north of Surbtion but not Waterloo. I hadn't started at Woking. It's only an issue for me because there is a 26 minute gap between stopping services from Surbiton at this time of the morning. I prefer to be on the move rather than waiting at stations for 20 minutes.
Now we have left running passengers delayed this train at Walton on Thames. That's no fault of the rail company though.
Edit: Although I heard an announcement about signalling issues once, the 8.02 was actually delayed today due to a train fault. It left Woking 14 minutes late and they decided to run it fast between Weybridge and Waterloo. Wonder if they would have been just as likely to have done that, had it been 7 minutes late leaving Woking. Bear in mind when it left 7 minutes late, it was 21 minutes late leaving Surbtion.
The 8.20 left Guildford on time but arrived into Woking 6 minutes late. Expect that to be delayed, delaying the 9.01 from Surbtion too. One waits 26 minutes for a stopping train and then two are due within 4 minutes when on time. I understand the reason for this being the case. At least they are announcing the next train to the stopping stations for passengers waiting at Surbtion.