Big opportunity missed
I think a big opportunity was missed recently. With the switch-over from analogue to digital broadcasting, it should have been mandated from day one that every receiver (including set-top boxes) must incorporate a smartcard reader, so that the BBC channels could eventually have been broadcast scrambled.
That would mean that if you didn't pay, you couldn't watch, and no need for enforcement mobs. It would also alter the payment model from per-household to per-set; but cards could be swapped about as required in houses with more TVs than people. It wouldn't necessarily be less fair, just different.
And I speak in the capacity of someone who lived for awhile without a TV set, and was falsely assumed to be watching without paying, and someone whose family income while growing up derived ultimately from the TV licence payer.