The route forms a major commuter route into London from Hertfordshire, Cambridgeshire, and eastern Bedfordshire; ridership has grown rapidly over recent years.
The Great Northern route is formed of the Northern City Line, Hertford Loop line, the southern section of the East Coast Main Line between London Kings Cross and Peterborough, the Cambridge line, and the Fen line.[10] Since Greater Anglia withdrew its services to King's Lynn in May 2023,[11] Govia Thameslink Railway has been the sole operator of the entire route except between London Kings Cross and Peterborough, and between Cambridge and Ely. The route serves 55 stations.[3]
London King's Cross to Cambridge - Six stopping and two (three on Saturday) semi-fast services from Monday to Saturday, one northbound and two southbound stopping services on Sunday. The fastest service took about 1 hour 30 minutes.
London King's Cross to Royston - Two (three on Wednesday) additional services from Monday to Saturday, one additional service on Sunday.
London King's Cross to Baldock - Seven additional services from Monday to Saturday.
London King's Cross to Letchworth - Three additional services from Monday to Saturday. The last service on Wednesday ran past midnight into Thursday morning.
Since the 1960s, Great Northern has been used to describe the suburban part of the East Coast Main Line, south of Peterborough and south of Royston. The Great Northern Railway had proposed electrification of part of the line in 1903, but it was not until 1971 that a scheme to electrify the line from London King's Cross and Moorgate was authorised.[14]
The Inner Suburban Lines to Welwyn Garden City and Hertford North were electrified in 1976 with Class 313 EMUs. In 1978 the electrification was complete to Royston with Class 312 EMUs providing the service. The route was then promoted as the Great Northern Electrics.[14] The route between Hertford and Langley Junction, south of Stevenage, was also electrified but not regularly used by electric trains until 1979, when one Moorgate - Hertford service per hour was extended to Letchworth Garden City; prior to this DMUs provided an infrequent service over this route, running between Hertford and Huntingdon / Peterborough. From 1979 until 1987 DMUs provided the service between Hitchin and Huntingdon/Peterborough. DMUs also provided a shuttle service between Royston and Cambridge between 1978 and 1988, connecting with the electric trains and replacing the former through Cambridge buffet expresses between Kings Cross and the university city.
With the further electrification of the East Coast Main Line between 1986 and 1988, electric services could be extended to Peterborough and the outer suburban service was changed from Class 312 to Class 317, some of which were cascaded from the newly created Thameslink route, with the remainder newly built.
In 1984[15] it was decided to electrify the line between Royston and Shepreth Branch Junction, a junction on the West Anglia Main Line north of Shelford, allowing the reinstatement of through services to Cambridge from London King's Cross via the East Coast Main Line, which was faster than the conventional route from Liverpool Street via the West Anglia Main Line. This electrification was completed in 1988. Later the track between these points was also upgraded with welded joint track instead of the jointed track that had existed, and the maximum line speed was raised to 90mph.
Rapid growth on the route, especially on the Cambridge Line resulted in consultation on a new service pattern,[16] which was then implemented at the timetable change in Spring 2009. During the peak hours, the route is now saturated and can support no further service improvements.
Together with the two-track Digswell Viaduct (Welwyn Viaduct) some ten miles to the south, the flat junction just north of Hitchin was a major bottleneck,[17] as northbound trains diverging from the East Coast Main Line towards Letchworth and thence to Cambridge had to cross one northbound (fast) line and two southbound (fast and slow) lines to access the Cambridge Line. Proposals as part of the original electrification work envisaged a new underpass here and land was set aside for its construction. However, budgetary constraints forced this part of the programme to be abandoned. The land stood empty for many years, but has since been used to provide new housing.
A new plan[18] and subsequent application for an order[19] to build a flyover was approved, and construction was completed in June 2013. The scheme has created a new single-track line that diverges from the northbound slow line at a new junction just beyond Hitchin station, using a short embankment section of the former Bedford to Hitchin Line, a section of which was cleared of vegetation and made progressively higher, to form a short ramp. The track is carried over the East Coast Main Line on a newly constructed viaduct and onto a new embankment to join the present Cambridge Line at the newly created Hitchin East Junction, closer to Letchworth. Although this takes trains over a longer distance, it removes the need for them to dwell at Hitchin – sometimes for several minutes – awaiting a path across the tracks of the main London-Peterborough route, thus decreasing the overall journey time to Cambridge in many instances. The scheme improves the punctuality and reliability of both the London-Cambridge and London-Peterborough routes, because Peterborough-bound stopping trains are no longer delayed if running closely behind a Cambridge service being held at Hitchin waiting to cross the flat junction.
As part of the Thameslink Programme,[20] the Great Northern Route has been connected to the existing Thameslink route via a new junction at Belle Isle[21] (south of the High Speed 1 flyover, just north of London King's Cross). Two single-bore tunnels (known as the Canal Tunnels) were driven from here to the low-level platforms at St Pancras during the 'St Pancras Box' phase of the redevelopment works that created St Pancras International station. Trains diverging from the Great Northern Route at Belle Isle join the 'core' St Pancras - Farringdon - City Thameslink - Blackfriars section of the existing Thameslink route and then serve stations across Surrey, East Sussex, Kent, and West Sussex.
On 6 November 2017 the first Thameslink Programme units entered service on the Great Northern route.[22] 700128 worked the 0656 Peterborough – London King's Cross and 1812 return, while 700125 worked the 0733 Peterborough – London King's Cross and 1742 return.[22]
Services
Off-peak
The Great Northern Monday–Friday off-peak service pattern, as of May 2025, with frequencies in trains per hour (tph), consists of the following:[23][24]
The additions to the above table during Monday-Friday peak hours, as of May 2025, consists of the following:[23][24]
During the morning peak, Great Northern operate 5 'limited stop' southbound-only services between Peterborough and London King's Cross. During the evening peak they operate 5 'limited stop' northbound-only services between London King's Cross and Peterborough. These 'limited stop' services to/from Peterborough call at Huntingdon, St Neots, Biggleswade and Stevenage only.
During peak hours, Great Northern operate 3 'limited stop' services in each direction between Letchworth Garden City and London King's Cross, with calls at Hitchin, Knebworth and Welwyn North only.
During peak hours, services between London King's Cross and Ely (see table above) are extended to/from King's Lynn, resulting in a 2tph service in both directions between London King's Cross and King's Lynn. Many of these peak hour King's Lynn services additionally call at Letchworth Garden City and Royston.
During peak hours, services between London King's Cross and Letchworth Garden City (see table above) are extended to/from Cambridge, resulting in a 2tph 'stopping service' in both directions between London King's Cross and Cambridge.
During peak hours, services between Moorgate and Welwyn Garden City (see table above) double in frequency, resulting in a 4tph service in both directions between Moorgate and Welwyn Garden City. 2tph out of these 4tph do not call at Harringay or Hornsey.
During peak hours, services between Moorgate and Stevenage via Hertford North (see table above) are supplemented by a 2tph service between Moorgate and Hertford North, resulting in a 4tph service in both directions between Moorgate and Hertford North. In addition, for just 1 hour in the morning peak, Great Northern operate a 2tph southbound-only service between Gordon Hill and Moorgate, and for just 1 hour in the evening peak, they operate a 2tph northbound-only service between Moorgate and Gordon Hill. So during this 1 hour period in both the morning and evening peaks, what results is a 6tph service between Moorgate and Gordon Hill (with only 4tph of these calling at Harringay and Hornsey), only running in the direction of the main commuting flow in/out of London.
Rolling stock
Govia Thameslink Railway
The majority of Great Northern services are operated with Class 387Electrostar units.[25] On 12 March 2024 it was announced that Great Northern would lease 30 Class 379 units from Porterbrook.[26][27] These were introduced for their services to Letchworth in February 2025,[28] which replaced Class 387 units in order to allow them to be transferred to Southern.[25]
A station to the south of Cambridge was first proposed in 2017,[35] and although its application to New Stations Fund 2 that year was unsuccessful,[36] the November 2017 budget allocated it £5 million in funding.[37] The station, called Cambridge South, is situated between Foxton and Cambridge on the Cambridge line, and will serve the Cambridge Biomedical Campus and the wider Trumpington area.[38] The station is set to open in early 2026, which is a delay from the originally proposed date of late 2025.[39] The station will be managed by Greater Anglia[40] and will be served by all Greater Anglia, Great Northern, Thameslink and CrossCountry services passing through the station when it opens.[41] Additionally, East West Rail services will also call at Cambridge South in the future, once East West Rail has been built to Cambridge and opened.[42]
East West Rail
The route of East West Rail, the new railway linking the cities of Oxford and Cambridge, will intersect with the East Coast Main Line at Tempsford in Bedfordshire, where a new station will be built to serve both routes. This has led to worry from local residents, particularly due to a report by East West Rail that the population of the village could grow from 600 to 44,000.[43] As a result of extra funding in the 2024 budget, East West Rail will deliver the station five years earlier than planned, allowing passengers on the East Coast Main Line to access the station before it opens as part of the East West Rail route.[44]
Both Cambridge South and Cambridge stations on the Cambridge line will also be served by East West Rail, the Bedford–Cambridge section of which is in consultation as of 2025.[45] The current plan for the route will include a grade-separated junction with the line at Hauxton, between Foxton and Cambridge. This will include improvements to Hauxton level crossing.[45] East West Rail confirmed in their 2021 consultation that the Cambridge line will remain double-tracked between this junction and Shepreth Junction, where the line will be quadrupled to run alongside the West Anglia Main Line as far as Cambridge.[42]
The last refresh of the lineside signalling system on the southern ECML between London King's Cross and the Stoke Tunnel was commissioned in 1977 and as such was up for renewal between 2020 and 2029. Instead of renewing the current lineside signalling, it was decided to upgrade this section of the ECML to ERTMS in-cab signalling. This will not be the first instance of ERTMS on the UK rail network; it is in use on the Cambrian Line (where it was first piloted), on the Thameslink core Widened Lines route (with an ATO overlay), and on the Heathrow branch of the Great Western Main Line. However, it is the most complex application yet; it is the first use in the UK of ERTMS on such a busy, mixed-traffic line, with freight, commuter, regional and InterCity services sharing as little as two tracks in the tightest sections.[46]
Unlike the Widened Lines route and the GWML, where ERTMS complements traditional lineside signals, the southern ECML will have its signals removed once the transition period to ERTMS is complete. This means that all trains running on the route will be required to be fitted with the appropriate onboard equipment.
The Class 800 series (LNER Azuma Classes 800 and 801, Hull Trains Paragon Class 802, Lumo Class 803), Thameslink Class 700 and Great Northern Class 717 fleets are fitted with ERTMS equipment from manufacture. The Great Northern Class 387 fleet is undergoing retrofit, with the first train sent to Worksop Depot in October 2022. Following its return to service in July 2023, the remaining trains will be retrofitted in Hornsey Depot.[47] The introduction of in-cab signalling will allow the ECML line speed to be increased to 140mph in some places. The Class 800 series trains were designed to reach this speed, but minor modifications will be required to remove the equipment that is currently limiting speeds to 125mph. There are currently no plans to retrofit ERTMS equipment to the InterCity 225 fleet, as they are expected to be withdrawn before the removal of the lineside signals; this means they will never reach their design speed of 140mph (225km/h) in service.
Works to commission new ETCS digital signalling on the line, along with the first test train under the new system, took place during the Early May Bank Holiday in 2022.[48] The new signalling system was approved by the Office of Rail and Road in March 2023, and gradually introduced on passenger services from 27 November 2023.[49] By November 2024, all passenger services were operated under ETCS signalling,[50] with traditional lineside signals completely removed on 18 May 2025.[51]
Network Rail used Beacon Rail owned Class 313 unit 313121 as a test vehicle for ERTMS on the Hertford Loop line.[52] The plan involved resignalling a 5+1⁄2-mile (8.9km) section of the double track route to allow existing passenger and freight services to work bi-directionally over the up Hertford Loop line, freeing the down line for ERTMS tests and evaluation.[53]
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