The company was the second largest created by the Railways Act 1921. The principal constituents of the LNER were:
The total route mileage was 6,590 miles (10,610 km). The North Eastern Railway had the largest route mileage of 1,757 miles (2,828 km), whilst the Hull and Barnsley Railway was 106.5 miles (171.4 km).
It covered the area north and east of London. It included the East Coast Main Line from London to Edinburgh via York and Newcastle upon Tyne and the routes from Edinburgh to Aberdeen and Inverness. Most of the country east of the Pennines was within its purview, including East Anglia. The main workshops were in Doncaster, with others at Darlington, Inverurie and Stratford, London.
The LNER inherited four of London's termini: Fenchurch Street (ex-London and Blackwall Railway; King's Cross (ex-Great Northern Railway); Liverpool Street (ex-Great Eastern Railway); and Marylebone (ex-Great Central Railway). In addition, it ran suburban services to Broad Street (London, Midland and Scottish Railway) and Moorgate (Metropolitan Railway, later London Transport).
The LNER owned:
- 7,700 locomotives, 20,000 coaching vehicles, 29,700 freight vehicles, 140 items of electric rolling stock, 6 electric locomotives and 10 rail motor cars
- 6 turbine and 36 other steamers, and river boats and lake steamers, etc.
In partnership with the London, Midland and Scottish Railway (LMS), the LNER was co-owner of the Midland and Great Northern Joint Railway, the UK's biggest joint railway, much of which competed with the LNER's own lines. The M&GNJR was incorporated into the LNER in 1936. In 1933, on the formation of the London Passenger Transport Board, the LNER acquired the remaining operations of the Metropolitan Railway Company.
The LNER was the majority partner in the Cheshire Lines Committee and the
Forth Bridge Railway Company.
It depended on freight from heavy industry in Yorkshire, the north east of England and Scotland, and its revenue was reduced by the economic depression for much of the early part of its existence. In a bid to improve financial efficiency, staffing levels reduced from 207,500 in 1924 to 175,800 in 1937. For investment to retain freight traffic, new marshalling yards were built in Whitemoor in Cambridgeshire, and Hull in Yorkshire to attempt to retain freight traffic.
Sir Ralph Wedgwood introduced a Traffic Apprenticeship Scheme to attract graduates, train young managers and provide supervision by assistant general manager Robert Bell for career planning. The company adopted a regional managerial system, with general managers based in London, York and Edinburgh, and for a short time, Aberdeen.
For passenger services, Sir Nigel Gresley, the Chief Mechanical Engineer built new powerful locomotives and new coaches. Later developments such as the streamlined Silver Jubilee train of 1935 were exploited by the LNER publicity department, and embedded the non-stop London to Edinburgh services such as the Flying Scotsman in the public imagination. The crowning glory of this time was the world record speed of 126 miles per hour (203 km/h) achieved on a test run by LNER Class A4 4468 Mallard.
In 1929, the LNER chose the typeface Gill Sans as the standard typeface for the company. Soon it appeared on every facet of the company's identity, from metal locomotive nameplates and hand-painted station signage to printed restaurant car menus, timetables and advertising posters. The LNER promoted their rebranding by offering Eric Gill a footplate ride on the Flying Scotsman express service; he also painted for it a signboard in the style of Gill Sans, which survives in the collection of the St Bride Library. Gill Sans was retained by the Railway Executive in 1949 and was the official typeface until British Rail replaced it in the mid 1960s with Rail Alphabet.
Continental shipping services were provided from Harwich Parkeston Quay.
The company took up the offer in 1933 of government loans at low interest rates and electrified the lines from Manchester to Sheffield and Wath yard, and also commuter lines in the London suburban area.