Royal Mail is in a shambles right now.
They used to deliver postmen and mail to each area by van, but due to their Covid restrictions, only the driver is allowed in each van.
Postmen that don't drive either have to wait for mail to be delivered to their homes, and they often have to walk back to the sorting office to get another sack of mail, and walk back to their route to deliver it.
This is putting intolerable pressure on posties who are simply unable to complete their allotted delivery loads in the working time they have, even with overtime, with an inevitable knock-on effect on deliveries nationwide.