[astonex]

>You can't get a NI number without proving who you are

That's not true either. You're sent your NI number just before 16 years old without providing anything.

Also, an NI number is just a number. There is no photo. How can you look at it and say it belongs to the person presenting it? And no you can't look up a passport or something in another system based on the NI number, because those other IDs aren't mandatory so the person might not have them.

The only way to really ID someone is to have mandatory photo ID, whether that be digital or not.

[matt-p]

How do you think HMRC know to send you a card? If they're giving them out like smarties to foreigners then they could simply... Not (a British person gets one as a function of having a birth certificate)