North British Railway in the context of "Tay Bridge disaster"

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.

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.

North Britain is a term which has been used, particularly between the 17th and 19th centuries, for either the northern part of Great Britain or Scotland, which occupies the northernmost third of the island. "North Britains" could also refer to Britons from Scotland; with North Briton later the standard spelling. Its counterpart was South Britain, generally used to refer to England and Wales.