Essentially a tender version of the Standard 4 Tank like 80135 and 80136, the 4-6-0 version of the British Railways Standard 4 design was intended for general passenger and freight use on lines where the usual "Black Five" and similar locomotives would be too large or heavy. 80 examples were built between 1951 and 1957 and were allocated to the London Midland, Western and Southern regions.

75029 was built in 1954 and was decidedly mobile during her service life, being allocated to depots across the Western region including Reading, Oxford and Swindon, with a stint in Wales at Machynlleth and Croes Newydd sheds in the early to mid sixties.

Painted in British Railways' Brunswick Green livery used on passenger engines, "The Green Knight" has been a stalwart of the North Yorkshire Moors Railway, including being passed to work to Whitby and Battersby on the national network. A crack in the firebox was identified in 2015 and she is currently awaiting attention.