I recently queried a simple tax matter by writing snail-mail to HMRC Newcastle and received a reply from a named official that raised more questions. But the only address on the HMRC letterhead was BX9 1AS.
Not being aware of any UK town that might be abbreviated BX, and there being no BX in my postcode directory, I phoned to confirm that a reply to BX9 1AS would be in order.
After a frustrating 15 minutes wrestling with menus and listening to music I was told that this postcode has been created recently to receive all incoming HMRC mail and that letters will be passed to whoever is available to reply. The mind boggles that someone thinks this will be an improvement on continuity of service and personal contact. I am not holding my breath for an early reply.