Punctuality and cancellations will be based on whatever the TOC uploads into the database overnight. That becomes the agreed day's timetable.
I believe that is one of the reasons why realtime trains defaults to not displaying the cancelled services, but only shows the amendments that would appear in journey planners and information systems...
So if someone accidentally cancels a train during the nightly database upload but it runs, it still counts against the performance figures? I speak from the fact that after Christmas, some trains were showing as cancelled via NRE live departures but actually were running.
Interestingly my travel was more disrupted today than yesterday when yesterday they had a high winds and today rain but no speed restrictions in place on the lines I use at least.
This morning my train was 13 minutes late into Clapham Junction and left their 15 minutes late! My next train to Surbiton was 6 minutes late and tonight my train from Surbiton to Woking was 15 minutes late. They announced at the station, via an automated system, it was due to electrical power supply problem at Portsmouth. However the train that formed my service was mostly delayed between Woking and Waterloo so unless there was congestion from earlier Portsmouth services, I doubt that was the reason! The next automated message I heard just said listen to further announcements, which suggested someone realised it wasn't that. On line the only report was that my train to Woking was delayed by the preceding train. That preceding train had no reason given.
South West Train are running a revised timetable tomorrow due to expected flooding. Trains west of Salisbury only running every 2 hours and Fulwell Tunnel might flood again. Away from the trains I'll be curious to see how the River Wey through Guildford copes. Last weekend it had flooded part of Millmead [a road running beside the River]