A Travelling Post Office (TPO) was a type of mail train used in Great Britain and Ireland where the post was sorted en route, used from 1830 to 1996, with non-TPO mail trains ending in 2024.
The TPO can be traced back to the earlier days of the railway, the first ever postal movement by rail being performed by the Liverpool and Manchester Railway (L&MR) on 11 November 1830. The Railways (Conveyance of Mails) Act 1838 obliged railway companies to carry mail, and thus specialised rolling stock was quickly provided; the first true TPO emerged that same year. Further innovations followed, such as the development of lineside apparatus for picking up and setting down mailbags while underway, and the use of dedicated mail trains. By 1914, there were 126 TPO carriages in operation throughout the United Kingdom, while numerous other nations had adopted the concept, wholly or in part, as well.
During the latter part of the twentieth century, rail mail was subject to various changes. In Britain, Rail Express Systems (RES) was formed during the 1980s to rejuvenate the market, streamlining and centralising rail mail services, resulting in TPO coverage decreasing over the following years. During the 1990s, the Royal Mail, Britain's main customer for TPOs, ordered 16 four-car British Rail Class 325 electric multiple units to replace locomotive-hauled counterparts in handling parcels. However, wider economic factors, including increasingly effective mechanical sorting methods in comparison to the TPO's manual sorting by hand, along with operational safety concerns, made it increasingly unattractive to continue operating such services. Accordingly, the night of the 9/10 January 2004 saw the final TPO services run in Great Britain, with the carriages themselves used then sold for scrap or to preservation societies. The final load of mail to be loaded aboard a travelling post office was the consignment by air from Scotland via Bristol airport, put aboard the TPO at Yatton Station, Somerset in the early hours of 10th January 2004.
After a hiatus, some mail and parcels traffic has now returned to rail - carried in bulk and not sorted en-route.