I've had Similar Experiences.
-Edmonton and Vancouver were okay
-London Heathrow was fantastic. When we landed we got bumped into the front of the passport check line/Customs. There were hundreds in line and we were in and out in 15 minutes. We also experienced this when we took the Eurostar FastTrain to Paris. On our way back to Edmonton, the Heathrow airport personal would open up ropes and bypass thru priority security, no problemo.
I guess it helps our little one at the time was a cute and he smiled at all the ladies