London and North Eastern Railway in the context of "LNER Class A3 4472 Flying Scotsman"

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.

King's Cross railway station, also known as London King's Cross, is a passenger railway terminus in the London Borough of Camden, on the edge of Central London. It is in the London station group, one of the busiest stations in the United Kingdom and the southern terminus of the East Coast Main Line to Yorkshire and the Humber, North East England and Scotland. Adjacent to King's Cross station is St Pancras International, the London terminus for Eurostar services to continental Europe. Beneath both main line stations is King's Cross St Pancras tube station on the London Underground; combined, they form one of the country's largest and busiest transport hubs.

The station was opened in King's Cross in 1852 by the Great Northern Railway on the northern edge of Central London to accommodate the East Coast Main Line. It quickly grew to cater to suburban lines and was expanded several times in the 19th century. As part of the Big Four grouping in 1923, it came under the ownership of the London and North Eastern Railway, who introduced famous services such as the Flying Scotsman and locomotives such as Mallard. The station complex was redeveloped in the 1970s, simplifying the layout and providing electric suburban services, and it became a major terminus for the high-speed InterCity 125. As of 2018, long-distance trains from King's Cross are run by London North Eastern Railway to Edinburgh Waverley, Leeds and Newcastle; other long-distance operators include Hull Trains and Grand Central. In addition, Great Northern runs suburban commuter trains around North London, Hertfordshire, Cambridgeshire and Norfolk.

The North Eastern Railway (NER) was an English railway company. It was incorporated in 1854 by the combination of several existing railway companies. Later, it was amalgamated with other railways to form the London and North Eastern Railway at the Grouping in 1923. Its main line survives to the present day as part of the East Coast Main Line between London and Edinburgh.

Unlike many other pre-Grouping companies the NER had a relatively compact territory, in which it had a near monopoly. That district extended through Yorkshire, County Durham and Northumberland, with outposts in Westmorland and Cumberland. The only company penetrating its territory was the Hull & Barnsley, which it absorbed shortly before the main grouping. The NER's main line formed the middle link on the Anglo-Scottish "East Coast Main Line" between London and Edinburgh, joining the Great Northern Railway near Doncaster and the North British Railway at Berwick-upon-Tweed.

Sir Herbert Nigel Gresley CBE (19 June 1876 – 5 April 1941) was a British railway engineer. He was one of Britain's most famous steam locomotive engineers, who rose to become Chief Mechanical Engineer (CME) of the London and North Eastern Railway (LNER). He was the designer of some of the most famous steam locomotives in Britain, including the LNER Class A1 and LNER Class A4 4-6-2 Pacific engines. An A1 Pacific, Flying Scotsman, was the first steam locomotive officially recorded over 100 mph in passenger service, and an A4, No. 4468 Mallard, still holds the record for being the fastest steam locomotive in the world (126 mph).

Gresley's engines were considered elegant, both aesthetically and mechanically. His invention of a three-cylinder design with only two sets of Walschaerts valve gear, the Gresley conjugated valve gear, produced smooth running and power at lower cost than would have been achieved with a more conventional three sets of Walschaerts gear.

LNER Class A4 4468 Mallard is a 4-6-2 ("Pacific") steam locomotive built in 1938 for operation on the London and North Eastern Railway (LNER) at Doncaster Works to a design of Nigel Gresley. Its streamlined, wind tunnel tested design allowed it to haul long-distance express passenger services at high speeds. On 3 July 1938, Mallard broke the world speed record for steam locomotives at 126 mph (203 km/h), which still stands today.

While in British Railways days, regular steam-hauled rail services in the UK were officially limited to a 90 mph (140 km/h) "line speed", before the Second World War, the A4s had to run significantly above 90 mph (140 km/h) just to keep schedule on trains such as the Silver Jubilee and The Coronation, with the engines reaching 100 mph on many occasions. Mallard covered almost one and a half million miles (2.4 million km) before it was retired in 1963.