> "David Cameron could force porn websites to shut down"
Could he? Really? I doubt it.
Business idea: external age-verification service for these sites to use. Single-login that replaces the "please click on the over-18 button" landing page, with age verification probably done via entering a credit card.
There are already many of those services. But many of those who are even trying to be serious just ask for a credit card to verify that you're of age. Not sure how else to check if someone is of age without massive privacy issues, especially since the 'potential' customer could just lie.
Confirming age would require sites to identify users, which is a non-starter. The sites would lose all their traffic from much larger markets than the UK.