The DYFFRYN ARDUDWY Post Town is a Postal Region within the historic Postal County of Merioneth
When addressing mail to properties within this area it is important to write DYFFRYN ARDUDWY in capital letters before the postcode.
You no longer need to write the postal county of Merioneth when writing an address but many still do because it's fun and avoids confusion when a postal town shares the same name.