GWR 4900 Class 5972 Olton Hall

Built in April 1937 at Swindon Works for the Great Western Railway (GWR), No. 5972 was first allocated to Carmarthen, South Wales where it remained until 1951. After being fitted with a three row superheater at Swindon Works, it was allocated to Plymouth Laira. Its last shed allocation was to Cardiff East Dock, before it was withdrawn in December 1963, and sold to Woodham Brothers, Barry for scrap in May 1964.[1][2]

Woodham Brothers sold the locomotive to David Smith and it moved to Horbury railway works in Wakefield in May 1981.[1][3][4] In 1994, it moved to Carnforth MPD for restoration, being steamed for the first time in 1998.[5]

In the Harry Potter films, the locomotive is depicted pulling the Hogwarts Express, a fictional train, made up of four (later five) British Rail Mark 1 carriages. Scenes were filmed at King's Cross railway station, the Glenfinnan Viaduct and the North Yorkshire Moors Railway — along with internal scenes on board the train.

Hogwarts Castle name plate

When filmed, Olton Hall carried a "Hogwarts Express" headboard on the smokebox, featuring the Hogwarts school crest. The same emblem is featured as part of the "Hogwarts Railways" sigil on the tender and carriages. It retained its GWR number of 5972, but with alternative nameplates fitted, naming the engine Hogwarts Castle. It is painted in a crimson livery — a non-standard colour, as GWR locomotives traditionally used green.[6]

Olton Hall was not the first locomotive to be re-liveried to appear hauling the Hogwarts Express. To promote the fourth Harry Potter book, Harry Potter and the Goblet of Fire, Southern Railway West Country Class locomotive 34027 Taw Valley was temporarily repainted and renamed. However, it was rejected by film director Chris Columbus as looking "too modern" for the film, but it carried the name and colour for some months afterwards.[7]

The renaming as "...Castle" has become a railway preservation joke: "...the Hall that thinks it's a Castle"—the Great Western Railway Castle Class engines were different and larger.

Three full-size replicas of the locomotive as No. 5972 Hogwarts Castle are at The Wizarding World of Harry Potter (Universal Orlando Resort). Two as part of the Hogwarts Express train ride[8] and the other is a static exhibit in the Hogsmeade area.[9] There are also static models at the other Wizarding World of Harry Potter locations in Hollywood[10] and Japan.[11]

In 2015, the locomotive was put on static display at Warner Bros. Studio Tour London - The Making of Harry Potter, near Watford,[12][13] and will be displayed there until Warner Bros' lease on the locomotive from West Coast Railways expires.

No. 5972 is sometimes used for work other than its "Hogwarts" duties. In May 2009, it was moved temporarily to the Gloucestershire Warwickshire Railway, and in July 2009, it was based at Tyseley Locomotive Works for use on some of the regular Shakespeare Express trains run by Vintage Trains during the summer. It returned to the Gloucestershire Warwickshire Railway during their annual Wizard's Weekend event in 2010. In late 2011 the locomotive was on static display in Hyde Park, London. Just before its boiler and mainline certificate's expired, on 7 June & 12 July 2014, it worked two final Wizards Express rail tours from Manchester to York with 5972 working the trains between Carnforth and York in both directions (as far as Hellifield on the return leg of June's trip).[14][15]