London King's Cross railway station in the context of "Battle Bridge"

The East Coast Main Line (ECML) is a 393-mile-long (632 km) electrified railway between its northern terminus at Edinburgh Waverley and southern terminus at London King's Cross. Peterborough, Doncaster, York, Darlington, Durham and Newcastle are on the line, which is a key transport artery on the eastern side of Great Britain running broadly parallel to the A1 road. The main line acts as a 'spine' for several diverging branches, serving destinations such as Cambridge, Leeds, Hull, Sunderland and Lincoln, all with direct services to London. In addition, a few ECML services extend beyond Edinburgh to serve other Scottish destinations, such as Stirling, Inverness, Dundee, or Aberdeen.

The line was built during the 1840s by three railway companies, the North British Railway, the North Eastern Railway, and the Great Northern Railway. In 1923, the Railways Act 1921 led to their amalgamation to form the London and North Eastern Railway (LNER) and the line became its primary route. The LNER competed with the London, Midland and Scottish Railway (LMS) for long-distance passenger traffic between London and Scotland. The LNER's chief mechanical engineer Nigel Gresley designed iconic Pacific steam locomotives including Flying Scotsman and Mallard, the latter of which achieved a world record speed for a steam locomotive, 126 mph (203 km/h) on the Grantham-to-Peterborough section on 3 July 1938.

An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or gas turbines, are classed as diesel–electric or gas turbine–electric and not as electric locomotives, because the electric generator/motor combination serves only as a power transmission system.

Electric locomotives benefit from the high efficiency of electric motors, often above 90% (not including the inefficiency of generating the electricity). Additional efficiency can be gained from regenerative braking, which allows kinetic energy to be recovered during braking to put power back on the line. Newer electric locomotives use AC motor-inverter drive systems that provide for regenerative braking. Electric locomotives are quiet compared to diesel locomotives since there is no engine and exhaust noise and less mechanical noise. The lack of reciprocating parts means electric locomotives are easier on the track, reducing track maintenance. Power plant capacity is far greater than any individual locomotive uses, so electric locomotives can have a higher power output than diesel locomotives and they can produce even higher short-term surge power for fast acceleration. Electric locomotives are ideal for commuter rail service with frequent stops. Electric locomotives are used on freight routes with consistently high traffic volumes, or in areas with advanced rail networks. Power plants, even if they burn fossil fuels, are far cleaner than mobile sources such as locomotive engines. The power can also come from low-carbon or renewable sources, including geothermal power, hydroelectric power, biomass, solar power, nuclear power and wind turbines. Electric locomotives usually cost 20% less than diesel locomotives, their maintenance costs are 25–35% lower, and cost up to 50% less to run.

The Metropolitan Railway (also known as the Met) was a passenger and goods railway that served London from 1863 to 1933, its main line heading north-west from the capital's financial heart in the City to what were to become the Middlesex suburbs. Its first line connected the main-line railway termini at Paddington, Euston, and King's Cross to the City. The first section was built beneath the New Road using cut-and-cover between Paddington and King's Cross and in tunnel and cuttings beside Farringdon Road from King's Cross to near Smithfield, near the City. It opened to the public on 10 January 1863 with gas-lit wooden carriages hauled by steam locomotives, the world's first passenger-carrying designated underground railway.

The line was soon extended from both ends, and northwards via a branch from Baker Street. Southern branches, directly served, reached Hammersmith in 1864, Richmond in 1877 and the original completed the Inner Circle in 1884. The most important route was northwest into the Middlesex countryside, stimulating the development of new suburbs. Harrow was reached in 1880, and from 1897, having achieved the early patronage of the Duke of Buckingham and the owners of Waddesdon Manor, services extended for many years to Verney Junction in Buckinghamshire.

Hatfield is a town and civil parish in Hertfordshire, England, in the borough of Welwyn Hatfield. It had a population of 29,616 in 2001, 39,201 at the 2011 census, and 41,265 at the 2021 census. The settlement is of Saxon origin. Hatfield House, home of the Marquess of Salisbury, forms the nucleus of the old town. From the 1930s when de Havilland opened a factory, until the 1990s when British Aerospace closed it, aircraft design and manufacture employed more people there than any other industry. Hatfield was one of the post-war New Towns built around London and has much modernist architecture from the period. The University of Hertfordshire is based there.

Hatfield lies 20 miles (30 kilometres) north of London beside the A1(M) motorway and has direct trains to London King's Cross railway station, London St Pancras railway station, Finsbury Park and Moorgate. There has been a strong increase in commuters who work in London moving into the area.

Edinburgh Waverley (also known simply as Edinburgh; Scottish Gaelic: Waverley Dhùn Èideann) is the principal railway station serving Edinburgh, Scotland. It is the second busiest station in Scotland, after Glasgow Central. The station serves as the northern terminus of the East Coast Main Line, 393 miles 13 chains (393.16 miles; 632.7 kilometres) from London King's Cross, although some trains operated by London North Eastern Railway continue to other Scottish destinations beyond Edinburgh.

Peterborough railway station serves the cathedral city of Peterborough, Cambridgeshire, England. It is sited 76 miles 29 chains (122.9 km) north of London King's Cross. The station is a major interchange serving both the north–south East Coast Main Line, as well as long-distance and local east–west services. The station is managed by London North Eastern Railway. Ticket gates came into use at the station in 2012.

Doncaster railway station is a principal stop on the East Coast Main Line, serving the city of Doncaster, in South Yorkshire, England. It is 155 miles 77 chains (251 km) down the line from London King's Cross and is situated between Retford and York on the main line. It is managed by London North Eastern Railway. It is the second busiest station in South Yorkshire (after Sheffield) and the fourth busiest in Yorkshire & the Humber.

It is a major passenger interchange between the main line, Cross Country Route and local services running across Northern England. It is also the point for which London North Eastern Railway services branching off to Leeds diverge from the main route, which continues north towards Edinburgh Waverley.

York railway station is a principal stop on the East Coast Main Line (ECML) serving the cathedral city of York, North Yorkshire, England. It is 188 miles 40 chains (303.4 km) north of London King's Cross and, on the main line, it is situated between Doncaster to the south and Thirsk to the north. As of June 2018, the station is operated by London North Eastern Railway (LNER). It is the busiest station in North Yorkshire, the third busiest in Yorkshire & the Humber and the sixth busiest in Northern England, as well as being the busiest intermediate station on the East Coast Main Line. In Britain's 100 Best Railway Stations by Simon Jenkins, the station was one of only ten to be awarded five stars.

The present York station was built during the 1870s after it had become clear that the old station, which could not facilitate through traffic due to its positioning, was a hindrance to long distance express services along what is now referred to as the ECML. Designed by the North Eastern Railway architects Thomas Prosser and William Peachey and built by Lucas Brothers, the station was built to be expansive and well-furnished from the onset, complete with a distinctive curved train shed. Upon its opening on 25 June 1877, it was the largest railway station in the world, possessing 13 platforms along with various amenities, including a dedicated hotel (now The Principal York). Various additional facilities, from lengthened platforms to additional passenger facilities such as tea sheds, would be built subsequently.

Darlington railway station is a principal stop on the East Coast Main Line, serving the town of Darlington in County Durham, England. It is 232 miles 50 chains (232.63 miles; 374.37 kilometres) north of London King's Cross. It is situated between Northallerton to the south and Durham to the north. Its three-letter station code is DAR.

The station is well served, because it is an important stop for main line services, with trains operated by London North Eastern Railway, CrossCountry and TransPennine Express. It is also the interchange for Northern Trains services to Bishop Auckland, Middlesbrough and Saltburn.