4464 Bittern is a London and North Eastern Railway (LNER) Class A4 steam locomotive. Built for the LNER and completed on 18 December 1937 at Doncaster Works as works number 1866, it received number 4464. After that it was renumbered 19 on 16 August 1946 under the LNER 1946 renumbering scheme, and finally 60019 by British Railways on 10 October 1948, after nationalisation. Of the 35 strong class, it is one of six to survive into preservation but it is one of only two currently scheduled to be certified for mainline use.

The LNER Class A4 is a class of streamlined 4-6-2 steam locomotive 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. Thirty-five of the class were built to haul express passenger trains on the East Coast Main Line route from London Kings Cross via York to Newcastle, and later via Newcastle to Edinburgh, Scotland. They remained in service on the East Coast Main Line until the early 1960s when they were replaced by Deltic diesel locomotives; they themselves proving to be worthy successors to the A4s. Several A4s saw out their remaining days until 1966 in Scotland, particularly on the Aberdeen – Glasgow express trains, for which they were used to improve the timing from 3.5 to 3 hours.