The United Kingdom's National Transmission System (NTS) is the network of gas pipelines that supply gas to about forty power stations and large industrial users from natural gas terminals situated on the coast, and to gas distribution companies that supply commercial and domestic users. It covers Great Britain, i.e. England, Wales and Scotland.
Ownership The transmission network is owned by National Gas, which is owned by Macquarie Asset Management. Agreement was reached in July 2024 for Macquarie to buy National Grid’s final 20% stake, giving Macquarie full ownership in the first quarter of 2025.
The changing ownership of the NTS reflects developments and corporate changes in the UK's gas and energy industries. Gas Council and area boards, 1962 – 31 December 1972 British Gas Corporation, 1 January 1973 – 24 August 1986 British Gas plc, 24 August 1986 – 1994 Transco plc, part of British Gas plc, 1994 – 17 February 1997 Transco plc, part of BG plc, 17 February 1997 – 1999 Transco plc, part of BG Group plc, 1999 – 23 October 2000 Transco plc, part of Lattice Group plc, 23 October 2000 – 21 October 2002 Transco plc, part of National Grid Transco plc, 21 October 2002 – 31 January 2023; renamed National Grid Gas plc on 10 October 2005 National Grid Gas plc, owned by Macquarie, BCI and National Grid, from 31 January 2023; renamed National Gas Transmission plc on 6 February 2023
History
Origins The system originated in the construction during 1962–3 of the high-pressure methane pipeline from Canvey Island (on the Essex coast) to Leeds. Imported liquefied natural gas (LNG) from Algeria was turned into gas at the Canvey terminal and supplied to the pipeline, providing eight of the twelve area gas boards with access to natural gas. The gas was initially used to manufacture town gas, either as a feedstock in gas reforming processes or to enrich lean gases such as that produced by the Lurgi coal gasification process.
The pipeline was in diameter and operated at 1,000 pounds per square inch (69 bar). The pipeline had of spur lines, supplying gas to area boards. +Methane pipeline spur linesArea boardSupply toDiameter (inches)Length (miles)North ThamesBromley/East Greenwich 'Tee'1415.5Bromley102.5Slough (from Reading spur line)South EasternEast Greenwich123SouthernReading849EasternChelmsford1219.9Hitchin87Dunstable68.5Watford (from Reading spur line)122.1West MidlandsColeshill1410.5East MidlandsSheffield1210North WesternManchester1424North EasternLeeds128 The Gas Council was responsible for this £10 million co-operative scheme and the construction details were a joint effort of the distribution engineers of the area boards.
LNG had first been imported to Canvey from Louisiana in February 1959, and piped to Romford gasworks as feedstock to a reforming plant.
UK natural gas Natural gas was discovered on the UK continental shelf in 1965 and production started in 1967. The development of offshore natural gas fields is shown in the following table. Shore terminals were built to receive, process, blend and distribute the gas. +UK sources of offshore natural gas, 1967–1985 FieldField typeLicensee or operatorDiscoveredFirst gas onshoreShore terminalWest SoleGasBPSeptember 1965March 1967EasingtonLemanGasShell/Esso, Amoco/Gas Council, Arpet Group, MobilApril 1966August 1968BactonHewettGasPhillips Petroleum, Arpet groupOctober 1966July 1969BactonIndefatigableGasShell/Esso, Amoco/Gas CouncilJune 1966October 1971BactonVikingGasConoco/BNOCMay 1968July 1972Viking (Theddlethorpe)RoughGasAmoco/Gas CouncilMay 1968October 1975EasingtonFortiesOil + associated gasBPOctober 1970September 1977St FergusFrigg (Norway)GasTotalEnergiesJune 1971September 1977St FergusFrigg (UK)GasTotalEnergiesMay 1972September 1977St FergusPiperOil + associated gasOccidental groupJanuary 1973November 1978St FergusTartanOil + associated gasTexacoDecember 1974January 1981St FergusBrentOil + associated gasShell/EssoJuly 19711982St FergusMorecambe BayGas + condensateHydrocarbons (GB)September 19741985Barrow With the assured availability of natural gas, a government white paper on fuel policyFuel Policy, Cmnd. 3438, HMSO, London (1967). in November 1967 proposed that natural gas should be immediately and more extensively exploited. The Gas Council and area boards began a ten-year programme to convert all users and appliances to operate on natural gas and consequently to discontinue the manufacture of town gas at local gasworks. In a pilot scheme, users on Canvey Island had been converted to natural gas in 1966.
Building the NTS To exploit the availability of natural gas and to provide for more widespread distribution, construction began of a major new transmission network which became the National Transmission System.John Ellis 'The Origins and Growth of the British Gas Plant Operations Department', 2014.
Feeder pipelines – England Gas from the West Sole field was first dispatched from the Easington terminal on the Yorkshire coast in July 1967, via Feeder No. 1 across the Humber to the East Midland Gas Board's gasworks at Killingholme. It was used to enrich low calorific value manufactured gas. Feeder No. 1 was extended to Totley near Sheffield where it connected to the 18-inch methane pipeline. UK natural gas first entered the NTS in July 1968.
Feeder lines from the North Sea gas terminals to the spine of the NTS were laid and brought into use as the shore terminals were constructed. +Initial feeder pipelines of the NTSFeeder No.DiameterLengthFromTo Operational1Easington terminalScunthorpe and Totley near Sheffield, where it connected to the original methane pipeline.July 1967/ July 19682Bacton terminalBrisley, Eye, Peterborough and Churchover near Rugby, where it connected to the original methane pipeline.August 1968336-inchBacton terminalRoudham Heath, Cambridge, Peters Green, Whitwell near Hitchin, where it connected to the original methane pipeline.October 1969436-inchBacton terminalGreat Ryburgh, King's Lynn, Audley and Alrewas near Lichfield.Autumn 1970536-inchBacton terminalYelverton, Diss, Stowmarket, Braintree, Chelmsford and Horndon, where it connected to the original methane pipelineAutumn 19716PaullPickering (see note), Westwood and Little Burden near DarlingtonAutumn 1971736-inchWisbechGosberton, Hatton, Old Warden, Tydd St Giles and Scunthorpe1972830-inchFormer Viking (Theddlethorpe) terminalHattonJuly 1972 The No. 6 feeder runs via Pickering which received gas from a treatment plant for the onshore Lockton gas field.
Feeder pipelines – Scotland North Sea gas first reached Scotland in Spring 1970 at Coldstream via an extension of the Leeds-Newcastle pipeline. This pipeline was then extended to Glenmavis near Coatbridge Lanarkshire (Feeder No. 12) where a natural gas liquefication plant was constructed.
A major set of pipelines were constructed in Scotland in preparation for arrival of gas from the Frigg gas field in 1977. From the St Fergus terminal in Scotland, two pipelines (Feeder No. 10 and No. 11) were laid via Bathgate to Partington and Bishop Auckland to connect to the NTS in England, a total pipeline length of . These lines were commissioned in 1976 and cost £140 million. Initially they carried gas from southern England into Scotland until the Frigg field began production via St Fergus in September 1977. Compressor stations are provided at intervals along the pipelines. A third 36-inch pipeline from St Fergus (Feeder No. 12) was completed in 1978, and a fourth pipeline (Feeder No. 13) in 1982.
Growth of the NTS The NTS was extended from Leeds to Newcastle upon Tyne in early 1969. This line was extended to Coldstream in spring 1970 and then to Glenmavis, near Coatbridge, Lanarkshire.
The Wales Gas Board received natural gas supplies in 1969 through a 24-inch line from Churchover (Rugby) to Swansea via Wormington (an extension to Feeder No. 2). North Wales was also connected in 1969 via a 24-inch/18-inch pipeline from Audley Cheshire to Maelor near Wrexham (an extension to Feeder No. 4).
The South Western Gas Board received natural gas at the end of 1970 from a 24-inch/20-inch pipeline from Wormington to Exeter (Feeder No. 14).
A 30-inch/24-inch extension of Feeder No. 3 runs to the west of London via Slough to Mogador, Surrey, and was commissioned in 1970. An extension of Feeder No. 5 runs from Horndon-on-the Hill, crosses the Thames at Tilbury and runs via Shorne to connect to Mogador, completing the South London ring main which became operational in early 1972.
In addition to these distribution pipelines, in 1971 the area boards began to supply natural gas directly to major consumers. For example, a 24-inch 17 mile 'spine' pipeline was constructed to ICI Ltd at Billingham (designated as part of Feeder No. 6), and the West Midlands Gas Board laid six similar 'spine' mains into industrial districts of Birmingham and the Black Country.
Most of the NTS was built from the late 1960s to the early 1980s. +Growth of the NTS 1966–1983YearsNTS mileageOperational gas terminalsCompressor stations1966/7320Canvey01968/9688Canvey Easington Bacton01970/11898Canvey Easington Bacton11972/32199Canvey Easington Bacton Theddlethorpe41974/52308Canvey Easington Bacton Theddlethorpe91976/72915Canvey Easington Bacton Theddlethorpe St. Fergus101978/93047Canvey Easington Bacton Theddlethorpe St. Fergus1119833200Canvey Easington Bacton Theddlethorpe St. Fergus14 Later (post-1983) feeder mains not described above include:
+NTS Feeder pipelines built after 1983Feeder No.FromToYear commissioned9EasingtonEast Ilsley1983–86BrocklesbyStallingborough10BathgateGlenmavisThruntonSaltwick11BathgateLongtown12KirriemuirLongtown via BathgateSt FergusAberdeen14BarringtonKenn South15LongtownWarburton198416BarrowLupton1983Stapleford TawneyStanford Le Hope (near Canvey Island)17TheddlethorpeHatton198818PeterboroughCambridge (via Huntingdon and New Wimpole)1988–94Isle of GrainGravesend2008Matching GreenRye HouseMatching GreenTilbury1990St NeotsLittle Barford19EasingtonPaull199120IlchesterChoakford198921MawdesleyAlrewas1992–2001CarnforthBurscough1992ElworthDeeside power station199422Goxhill and HattonPeterborough199323ChurchoverHoneybourne1998–2001PeterstowGilwern2000WormingtonCorse200024St FergusLochside2001EasingtonPaull2010Hatton Silk Willoughby200125Bridge FarmMickle Trafford200126HuntingdonSteppingley200127BactonKing's Lynn2003CambridgeMatching Green200228HerbrandstonCorse200729EasingtonNether Kellett2006–08
The NTS now comprises over 7,600 km of welded steel gas pipelines. The Canvey to Leeds line is no longer part of the NTS.
LNG storage sites In addition to the Canvey Island liquefied natural gas (LNG) import terminal, further LNG storage sites were constructed from the late 1960s. These were peak-shaving facilities used to support the NTS at times of high demand, and to ensure security of gas supplies at strategic locations. When demand was high, liquefied natural gas was pumped from storage tanks, heated in vapourisers to a gaseous state and delivered into the NTS. When demand was low, gas was withdrawn from the NTS and liquefied by cryogenic cooling to minus 162 °C to replenish the storage tanks.