Three of my last 10 BA flights left within 15 minutes of scheduled departure time.

When planning shorthaul flights into/out of LHR, I now assume doors will open within one hour of scheduled arrival time for morning/early afternoon flights and within two hours for later afternoon/evening flights. I make my flight choice based on this, rather than schedule, which makes for a less frustrating experience.

(I realise I my “regular” routes and times of day may be particularly bad)