The - rather costly - present wot I ordered for Sarah from Amazon has failed to arrive. Amazon say they sent it to me on December 2nd, and advised me to contact the local Royal Mail Delivery Office.
The local Royal Mail Delivery Office say that actually a.) it's not classified as "lost" until 15 days after the due date (nearly there but not quite), and b.) even when it is lost, it's up to Amazon to claim compensation from the Royal Mail.