Having seen the queues at T5 at the weekend I wondered when this would come up...
It's not really due to
"It's all the people," he told me. "A lot of planes landed at once."
As radeng says it seems that in the wake of Teresa May sacking at least one very high ranking Border Control official everybody in Border Control has suddenly decided to be extra extra vigilant in examining passports.....given the buck passing that went on I can't say I blame them.....
(It doesn't help that IRIS is/has been decommissioned and the biometric gates didn't seem to be working well the other day)