https://preservedbritishsteamlocomotive ... lton-hall/
More latterly, 5972 Olton Hall has gained fame as the locomotive used in the Harry Potter film series. Owned by David Smith and painted red following its restoration to working order, the locomotive was selected for use as the engine for the ‘Hogwarts Express’ in 2001 and subsequently used in filming at Leavesden Studios,Kings Cross and also on the West Highland Line between Mallaig and Fort William between 2001 and 2010, painted in the fictitious ‘Hogwarts Railway’ livery and renamed as Hogwarts Castle. It currently carries a 10A (Carnforth) shedplate in recognition of its current home at Carnforth, although it often appears elsewhere in service or on display. 5972’s boiler certificate expired in 2014.
The locomotive is now on static display at The Harry Potter Museum at Warner Brothers Studios in Leavesden, near Watford and will remain there in the museum for two years.