Originally Posted by
Saracen
Not quite. I agree it's not an actual preventative measure, but it does allow reputable companies to screen their outgoing calls against it, which should, if they play the game fairly, prevent many/most such calls. Sadly, not everyone does play the game fairly and it's entirely ineffective against foreign call centres working for non-UK companies. But it's a semi-practical measure, not just a legal one.
It's by no means perfect, but broadly, effective.
What's even more effective is being very selective about who you give your phone number to in the first place. It's astonishing how many people ask for it. With me, vanishingly few get it.