Heathrow is the largest British airport by far. The second-largest, Gatwick, pre-emptively cut a whole bunch of flights in July and August about a month before Heathrow decided to do the same, the third largest is apparently Manchester which I think has been having problems for months (so much so that they no longer even make the news anymore), and so on. Iut doesn't seem to be isolated to the UK either, I've been hearing about very similar problems elsewhere in Eruope from people travelling there.