Last year, there was an AM Peak 12-coach 375 that was terminating at Blackfriars - one of the Southeastern peak services. They normally terminate in 3 or 4 as they are the bays, but on this particular morning, the train was routed into Platform 2. This is signalled as a bi-directional platform, but the preferred option for Northbound terminators is to run them empty to City Thameslink and turn them around there. As 375s are restricted north of Blackfriars, the only route was south. This wouldn't have been a problem, had the 700 sitting behind it not fouled the points on the approach to 2.
Because the 700 behind it had to reverse to Elephant, it ended up slowing down the Morning Peak by about 20 minutes. Apparently, the driver accepted it because, whilst it is an unusual route, the drivers are signed to use 1 and 2 - and could use them if, say, the points into 3 & 4 had seized-up or anything else that makes the bays inaccessible.