Despite not having permission for their visit in 2011, this site has a very nice collection of photos of the MailRail system taken by SilentUK.
See some more photos taken at Mount Pleasant station, and loads more of other underground sites of various types mainly around the UK.
Mainly about London Undergrounds disused stations & lines. Some additional information on other tunnels beneath London, including MailRail.
Check out More of David's Photos at his 'Rail Road photos' web page, also why not take a look at the Salem Hillsborough Railroad on which David regularly works.
Have a look at Hywel Williams page, all about the changing history of the Tube. Find out where those disused stations are, Have a look inside disused sections of the tube.
Have a look at Dewi Williams website about another tunnel under the streets of London, this one was built for trams and it actually crosses over the Post Office Railway at one point. Whilst there do have a look at the rest of Dewi's site
The archive of Royal Mail from 1636. Including, stamps of Great Britain from the Penny Black, British postal markings, letterboxes, vehicles, uniforms, sorting frames, sorting machines and handstamps. The Museum have rescued examples of stock from the Post Office Railway for preservation. A promotional video can be seen on the Youtube Website.
Royal Mail invites you to check out their latest collection of stamps. See what the future holds for the Post Office.