The line was originally built as a branch of the London, Tilbury and Southend Railway and opened on 7 June 1893 providing the LT&SR with a link to the Great Eastern Railway at Romford and a small goods yard where the branch joins the Great Eastern Main Line. At Romford the branch had a separate station entrance in a three-storey building opposite the Great Eastern station entrance and a cast-iron footbridge was constructed over South Street which opened when a LT&SR train was due. When in April 1934 the LT&SR building ceased use as a station and the ground floor was rented as a shop, the then London and North Eastern Railway took control of the whole station. junction diagram showing the line between Romford and Upminster Emerson Park Halt was opened on 1 October 1909. A run-round loop was constructed 500 yards to the west to enable extra trains to run between Emerson Park and Upminster. When push-pull working began in 1934 the loop was no longer required and was removed in circa 1936. From 17 September 1956 a diesel multiple unit from replaced the steam service and from 20 April 1957 a new bay platform, numbered six, opened at effectively making it part of the Great Eastern route. There were some attempts to close the line in the 1960s, but these failed. It was later electrified, and electric trains began operating on 17 April 1986. The line transferred to become part of the London Overground network in May 2015.
Infrastructure
The branch is known colloquially as the "Romford Push and Pull" as it is single-track throughout. It is electrified at 25 kV AC. Electrification of the line saw an end to years of speculation about its future. There is only one intermediate station, at Emerson Park. At the connection west of the station to the main line was severed in 1968. The branch has just one signal, on approach to Romford. There were plans to link the line from platform six at Upminster to the reception tracks of the London Underground depot there. This would have allowed the transfer of London Underground D78 Stock units onto the main line to be hauled away by diesel locomotive for refurbishment at the Ilford depot. These plans were scrapped when the refurbishment work was transferred to Wakefield in Yorkshire and the transfer was done by road. The point-work which was half installed is still visible from the eastern end of platform five at Upminster.
Services
The line is entirely within Travelcard Zone 6. Services are currently operated by London Overground, which replaced the previous operator, Abellio Greater Anglia, in May 2015. Trains are typically formed by a Class 315 with new Bombardier Aventras starting. As of December 2015, the service pattern on the route is one train every 30 minutes between approximately 6:15 am and 10 pm Mondays to Saturdays, and approximately 8:30 am and 8 pm on Sundays. The journey time from one terminus to the other is approximately nine minutes.
Geology
During the construction of the railway in 1892, the geologist T. V. Holmes discovered a five-metre layer of boulder clay underlying the gravel and sand in a section just north of St. Andrew's Park. This is now the Hornchurch CuttingSite of Special Scientific Interest, which exhibits the southernmost limit of the Anglian ice sheet 450,000 years ago, the furthest south that any ice sheet reached.
