Most of the former LNER Class A1 locomotives designed by Sir Nigel Gresley had been rebuilt as LNER Class A3 locomotives prior to this class being conceived. The few straggling LNER Class A1 locomotives that remained unrebuilt during the tenure of Peppercorn's predecessor, Edward Thompson, were redesignated by him as Class A10s in preparation for the construction of his new Class A1 locomotives. Thompson rebuilt the pioneer LNER pacific Great Northern in 1945; originally this was the new Class A1, but the rebuild was not repeated. Instead, initiated by Thompson but largely taken forward by his successor Arthur Peppercorn, Great Northern was designated Class A1/1, and a new class of Peppercorn A1s ordered.
The locomotives were designed to cope with the heaviest passenger trains in the after-war period on the East Coast Main Line (London – York – Newcastle – Edinburgh – Aberdeen) which consisted normally of trains with up to 15 coaches and up to 550 tons. The Peppercorn A1s were able to pull such a train on the flat at a speed of 60–70 mph (95-110 km/h). Like previous LNER pacifics, the class had a 3-cylinder arrangement. The chimney system was of the type Double-Kylchap.
Names of people: W. P. Allen (an LNER locomotive driver who became a member of the Railway Executive in 1948), Archibald Sturrock, Patrick Stirling, H. A. Ivatt, Sir Vincent Raven, Wilson Worsdell, Edward Fletcher (Locomotive Superintendents of pre-grouping railways), Sir Walter Scott, Saint Mungo
Names related to the works of Sir Walter Scott: Meg Merrilies, Hal o’ the Wynd, Kenilworth, Guy Mannering, Marmion, Borderer, Madge Wildfire, Redgauntlet, Bonnie Dundee. Some of these names had previously been used on NBR J class locomotives
Pre-grouping railway companies: North Eastern, Great Central, Great Eastern, North British
Place-related names: Balmoral, Abbotsford (Sir Walter Scott's house), Midlothian, Holyrood, Bon Accord (motto of Aberdeen), Auld Reekie (a soubriquet for Edinburgh), Saint Johnstoun (an old name for Perth), Aberdonian
None of the original production run of 49 Peppercorn A1s survived the scrapyard to be preserved, however in 2008 a brand new 50th A1 based on the Peppercorn patterns, 60163 Tornado, was completed as the evolved member of the class.
^Ian Allan ABC of British Railways Locomotives, summer 1961 edition, part 4, pp 26-27 )Names of 60114-60162 are given but it also includes the LNER Thompson Class A1/1 60113 Great Northern in the list, making 50 locomotives.)
^"New steam loco ready for service". BBC News. 19 November 2008. Retrieved 19 November 2008. The first new steam engine to be built in the UK for almost 50 years is ready for service after successfully completing all its trial runs ... Tornado, a Peppercorn class A1 Pacific steam locomotive ...
^Trevena, Arthur (1981). Trains in Trouble: Vol. 2. Redruth: Atlantic Books. p. 34. ISBN0-906899-03-6.