My new "black" passport did not work last week in LHR T5. Didn't help that the person at the front of the queue for the failures had a really complex situation (Home Office error) and held the queue for 20 minutes.

My previous burgundy passport worked only once at a UK airport in the entire time I had it. All the other times I was told that I share my name with a wanted person and that I'd always be flagged.

If "technique" is the problem, why didn't it work when the attendant inserted the passport in the machine for me? Surely they're experts. The attendant had me try it in four different gates.