Below are the names and numbers of the steam locomotives that comprised the LNER Gresley Classes A1 and A3, that ran on the Great Northern (GNR) and latterly the London and North Eastern Railway network. They represented Nigel Gresley 's attempt to standardise steam design.

The London and North Eastern Railway Gresley Classes A1 and A3 were 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley for passenger work. They were initially intended for use on the Great Northern Railway (GNR), but became a standard design on the London and North Eastern Railway after the amalgamation of 1923.

The LNER Class A4 is a class of streamlined 4-6-2 steam locomotives designed by Nigel Gresley for the London and North Eastern Railway in 1935. Their streamlined design gave them high-speed capability as well as making them instantly recognisable, and one of the class, 4468 Mallard, holds the record as the world's fastest steam locomotive.

The A0 is a 'what if' 4-6-2 Pacific locomotive design that was as far as we know drawn by Sir Nigel Gresley in 1915 and a couple of known redrafts in the early 20's afterwards.

Now for Gordon's true origins - the fictional side of the A0 Pacific locomotive story. We believe he is in fact the A0 design, albeit rebuilt and modified to a mechanically identical, but outwardly unique, locomotive.

Of note is its unusual and possibly unique outer cylinders, and a large Ivatt cab we believe is shared with the original A0 design (and, like the A0 to A1 design here, found to be wanting by engine crews and modified significantly for the production variant O2 locomotives).

This section of the LNER Encyclopedia describes all of the locomotive classes to serve with the LNER. The LNER would often denote major modifications with a slash. E.g. B16/2 is a …

Between 1923 and 1925, 51 A1 locomotives were built; twenty by the North British Locomotive Company, and the remainder by Doncaster Works. However, Gresley's Pacifics had been designed to work within the bounds of the Great Northern Railway, meaning maximum distances of less than 200 miles (322 km).

The London and North Eastern Railway LNER Gresley Classes A1 (A10) and A3 locomotives represented two distinct stages in the history of the British 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley.

London and North Eastern Railway 's (LNER) Peppercorn Class A1 is a class of 4-6-2 "Pacific" steam locomotives largely built between 1948 and 1949 at Doncaster and Darlington Works to a design of Arthur Peppercorn.