It's a combination of luck and the time you pass through. Outbound through T2 security today (1st) there was no delay at all for me. Straight through. Staff chatty and friendly as well; they often get a bad rap on here.
Returned through T1 just after midnight. Probably a couple of minutes queue at UK Border. All went very smoothly. Staff there were very friendly as well.
I'm aware that these departments have difficult moments, but we should acknowledge that there are also long periods where everything goes to plan. I couldn't fault the airport staff today. Top notch. Likewise aboard TUI (out) and EasyJet (back).