I visited Olympia yesterday for the Great British Beer Festival. Arrived at Embankment expecting there to be no Olympia service at all (as is usual for the GBBF) and planned either to go to West Brompton then Overground to Olympia or simply walk from West Kensington (depending how I felt, how hot it was etc.). Imagine my surprise when I saw the train indicator at Embankment with a direct service terminating at Olympia. It wasn't a one-off as there seemed to be a service about every eight minutes or so (which was still running when I returned at about 6pm, my train terminating at Tower Hill). I know there were problems between Plaistow and Dagenham yesterday, so was Olympia used to terminate trains to help cope with that? I noticed there were no through trains from the "main line" to Wimbledon that I could see.
I'd have thought that when they can't run Districts east of Aldgate, and hence turn at Tower Hill (so needing to thin out the service given the single reversing platform at TH), then they need to run as many as possible to their normal western destinations, in order to diminish the service to those destinations as little as possible. So turning some at Olympia seems strange (if the signal failure out east was indeed the reason for the Olympia services). So was it, rather, that they had specifically scheduled some Olympia trains for the GBBF? (Though the normal Olympia service runs just from High St Ken ... so that doesn't make much sense either.) Also - an 8-minute-interval service to Olympia is unheard of...
On the other hand, I was on the trunk section of the District one day recently - a normal weekday when there wouldn't normally be any Olympias at all - when there was disruption on one of the
western branches. On that occasion, there were odd ones from the trunk going to Olympia - which
did make sense so as to have somewhere to turn them and maintain the frequency in the centre.