Well that’s not really true. It’s not like cash is deanonynising because of the serial numbers. You can still get stamps on a grey market or send someone else to get them for you, and I’m sure they’re sold in lots of places that don’t have CCTV. The postmark would always have identified the approximate source location, it’s just a bit more precise now.
You can keep your privacy, but most people will not bother. Most people will buy stamps with a card (or phone) payment so there is a complete chain of identify.
The aim is mass surveillance so a few people going to the trouble of avoiding it is not a problem. True, it is meta data (not letter contents) but we know that is pretty powerful by itself.
I do mean it is the aim - they never really explained what the real advantages of doing it for, and I suspect there is pressure from the security services who are accustomed to seeing most communications (or at least most meta data) to seal what they see as a hole in data collection.
Using cash to buy them is not hard and the odds of anyone going through the CCTV is low unless you are going to post anthrax to the PM or something. I imagine the main reason to do it was to make it harder to use fake stamps, although there may be some tracking going on.
When you send a letter, it's usually stamped by the post office you are sending it from, so you already gotta do a bit of work to stay anonymous when sending things out. And in the CCTV-loving land of the brits, I gotta imagine there's cameras on every postbox in the country
You now have to be more careful about buying the stamps themselves though. You could make a stock of them and not use them for a year or so (not like CCTV footage lasts more than a week).
It links to identity of whoever purchased them with credit card. Or whoever stood in front of the camera when transaction for these stamps was registered.
I'd bet money in a forensic scenario they could look up the batch and then estimate the sequence and thus date of sale and pull the post office cctv footage.
