I think its to help with manual sorting. Letters received need only have the W1 ...

		Symbiote on April 12, 2022 \| parent \| context \| favorite \| on: Why the Gov.uk Design System team changed the inpu... I think its to help with manual sorting. Letters received need only have the W1 part read, to see where they should be sent. When they reach Westminster, the 1AA part is read to sort them for final delivery.