Too late to edit ^^^ but I am intrigued to see that the Grauniad saw fit to ‘re-correct’ its previous description of the code used on the stamps.
If it looks like a QR code, and reads like a QR code …. 
MichaelG.
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[quote]
This article was amended on 21 February 2022 to restore the article’s original description of the new stamp feature as a barcode, and remove “corrections” (to text, and in a 3 February footnote) that erroneously renamed the feature a QR code. A line has also been inserted defining the type of barcode used.
[/quote]
Edit: __ One lives and learns :
https://www.neodynamic.com/barcodes/
Edited By Michael Gilligan on 07/12/2022 09:30:24