Its numerous branches also connect the main line to Southminster, Braintree, Sudbury, Harwich and a number of coastal towns including Southend-on-Sea, Clacton-on-Sea, Walton-on-the-Naze and Lowestoft.

The line is also heavily used by leisure travellers, as it and its branches serve a number of seaside resorts, shopping areas and countryside destinations.

The route also provides the main artery for substantial freight traffic to and from Felixstowe and Harwich, via their respective branch lines.

The first section of the line, built by the Eastern Counties Railway (ECR), opened in June 1839 between a short-lived temporary terminus at Devonshire Street in the East End of London and Romford, then in the Havering Liberty in Essex.

The London terminus was moved in July 1840 to Shoreditch (later renamed Bishopsgate), after 1900 in the Metropolitan Borough of Bethnal Green, and at the eastern end the line was extended 6 miles (9.7 km) out to Brentwood in the same year.

The section of line between Colchester and Ipswich was built by the Eastern Union Railway (EUR) to standard gauge and opened to passenger traffic in June 1846.

It was also in this year that two extra tracks were added between Bethnal Green and Liverpool Street which were for the use of West Anglia Main Line services.

In 1902, the quadruple track was extended from Seven Kings to Romford, but it wasn't until 1913 that four-tracking out to Shenfield was suggested and the First World War caused delay to this plan.

In the 1930s, a flyover was constructed just west of Ilford to switch the main and electric lines over, to enable main line trains to utilise Liverpool Street's longer west side platforms without having to cross east side suburban traffic in the station throat.

Either side of the Ilford flyover there are single-track connections between each pair of lines, with the westbound track extending to Manor Park and just beyond.

Plans were drawn up in the 1930s to electrify the suburban lines from Liverpool Street to Shenfield at 1,500 V DC and work was started on implementing this.

However, the outbreak of the Second World War brought the project to a temporary halt and it was not until 1949 that the scheme was completed with electrification being extended to Chelmsford in 1956.

[11][12] The British Railways 1955 Modernisation Plan called for overhead line systems in Great Britain to be standardised at 25 kV AC.

[13] By the late 1970s, the costs of running the dated mechanical signalling systems north of Colchester was recognised and, in 1978, a scheme for track rationalisation and re-signalling was duly submitted to the Department of Transport.

The system uses BR Mark 3 solid state interlockings, predominantly four-aspect signals and a combination of Smiths clamp-lock and GEC-Alsthom HW2000 point machines.

The GEML has a loading gauge of W10 between Liverpool Street and Haughley Junction (approximately 13 miles 63 chains north of Ipswich) and from there is W9 to Norwich.

The GEML has six tracks up to the London-end of Stratford and the junction to Temple Mills; there are five lines through the station, dropping to four at the country end.

There are several locations where the route has more than two tracks, predominantly through stations such as Colchester and Ipswich, along with goods loops, such as at the London end of Ingatestone.

There is also a short stretch of single track on approach to Norwich, as the line passes over the River Wensum on the Trowse Bridge.

[28] During the excavation of the tunnel, many important fossils were discovered, including rhinoceros, lion and mammoth; the site was known as the "Stoke Bone Beds".

Due to this, as well as traffic demands growing throughout the 21st century, the traction supply feeding arrangements are complex and somewhat unintuitive with several seemingly redundant features.

The low voltage AC utilised broadly the same substations, grid connections, OLE components and electrical clearances as the previous DC system.

In 2022, a small section between Bow Junction and Gidea Park was upgraded to a 2x25kV AC autotransformer system in order to support the Elizabeth Line service.

Pudding Mill Lane ATFS also feeds the Crossrail core from that point to the Westbourne Park tunnel portal and towards Abbey Wood.

Electric locomotives replaced diesel haulage from the mid-1980s, when the remainder of the GEML was electrified north of Colchester; their utilisation continued until March 2020.

Push-pull services were introduced during their tenure, initially using a DBSO coach at the Norwich end and latterly with Mark 3 Driving Van Trailers, cascaded from the West Coast Main Line.

Freight services also operate frequently on the Great Eastern Main Line, with its easy access to the Port of Felixstowe.

A limited number of weekend (and when engineering work is planned) c2c services, operate on part of the line between Stratford and Liverpool Street.

Branch lines diverge at Romford, Shenfield, Witham, Marks Tey, Colchester, Ipswich, Stowmarket and Norwich.

Additionally, a very limited number of main line services call at Ilford, Seven Kings and Gidea Park during early mornings and late nights, often for the convenience of train drivers who may be working from these locations.