Chathill is a hamlet in Northumberland about 9 miles north of Alnwick. In the nominal roll of Northumberland it is recorded as a Headquarters address.
It was used by the Auxiliary Units in Northumberland for secret mail between them and the higher command. It is not far from Seahouses which was the Northumberland Headquarters for a while and the original training ground near Belford (Shielow Castle) where Anthony Quayle had his Headquarters.
The Post Office is at the end of the north bound platform of Chathill railway station which would make sending messages to HQ in Darlington, York and further a field easy and you could probably get a reply within a couple of hours by the next north bound train. Though not as famous as Highworth P.O. it certainly played it`s part.