When British Railways were nationalised and the LNER A4s were renumbered, 60033 Seagull and two of her sisters E22 Mallard and 60034 Lord Faringdon were used for the 1948 Locomotive Exchange Trials.

Seagull, Doncaster Works number 1876, was fitted with a Kylchap double blastpipe as from new, never having a single chimney.

In her service life she wore a variety of liveries with different numbering schemes: Garter Blue as 4902 from her introduction, LNER black as of 27 May 1942, wartime black marked on tender as "NE" from 24 September 1943, renumbered as E33 on 31 October 1946, garter blue with no valances as of 5 December 1947, renumbered as 60033 on 10 April 1948, British Railways dark blue on 10 November 1950 and finally British Railways Brunswick green on 13 June 1952.

All of the class were fitted with streamlined valances, or side skirting, from new, but these were removed during the war to ease maintenance.

Seagull was fitted with three tenders during her career: 5636 (28 June 1938 – 30 March 1948), 5325 (9 April 1948 – 28 May 1954) and 5332 (28 May 1954 – 29 December 1962).