In 1844 Peterborough was a small market town into which two road mail coach services ran up and down each day. In 1845 this small market town grew rapidly after it was served with a railway line from Blisworth on the London & Birmingham Railway. This line ran east from Blisworth through Northampton, Wellingborough, Thrapston, Oundle, Wansford (Sibson) and into Peterborough. This was the very first railway route into London and so important was it to the townsfolk of Peterborough and the surrounding area, that on the day in June 1845 the line opened for passenger traffic the population of the city doubled.
The Post Office authorities were quick to recognise the potential of this railway service and by December 1845 a contract was drawn up to have mails conveyed over the line. The road coach services between Lincolnshire and London were truncated at Peterborough and the mails and passengers taken the rest of the way by train. At first the significance of the relationship between rail and mail did not manifest itself to the good burghers of Peterborough or for that matter the Post Office.
Shortly after the London & Birmingham line from Blisworth arrived in Peterborough, the Eastern Counties 'Ely & Peterborough' line opened in 1846 with an end on connection. In fact the London & Birmingham line used the Eastern Counties station in Peterborough before the owning company. The Midland Counties 'Syston to Peterborough, line (fully opened in 1848) had its own station but it was short lived and they too used the facilities at the Eastern Counties station. Finally, the defining railway construction took place when the Great Northern Railway built its lines from Doncaster via Lincolnshire (opened 1848), from London to join up the route to Doncaster (opened 1859) and then the direct through route "Towns Line" via Grantham, Newark and Retford (opened in 1852).
Within seven years Peterborough, the sleepy little market town, had become a very important railway junction having rail access to all parts of the country. Each one of these railway companies was contracted to convey mails and over the years a TPO, District Sorting Carriage or Bag Tender served each of the aforementioned routes at some period.
Peterborough Post Office, due almost entirely to the railways, grew from a tiny one roomed Receiving Office with one elderly lady Letter Carrier to one of only thirteen great General Forwarding Offices. Almost from the very beginning Peterborough Post Office was served by TPO services and it is this long association between mail and rail, and in particular the TPO system, that the Nene Valley Railway is seeking to perpetuate.