The flight deck, on one of the few Easyjet flights from Schonefeld last Thursday evening, said that the cause of that day's upset was ATC disruption by IA in France and Spain.
That flight, to LGW was delayed but not very significantly. A lot on the board (6 - 7?) showed CANCELLED. Nearly all Easyjet, but they had the majority of flights on the board anyway.
Sounded plausible, and they made good time finishing with a westerly landing at LGW.