In May 2013, at the request of London Underground, the locomotive was painted in red London Transport livery and numbered L.150, to commemorate the 150th anniversary of the Metropolitan line, and between 25-27 May it operated special trains between Harrow-on-the-Hill and Amersham, along with Met 1, 9466 and Sarah Siddons.

The Great Western Railway (GWR) 4575 Class is a class of 2-6-2T British steam locomotives.

No. 5521 is a GWR 4575 Class or 'Small Prairie' 2-6-2T steam locomotive built for the Great Western Railway (GWR). They were designed as small mixed traffic branch tank engine locomotives, mainly used on branch lines all over the Great Western Railway system.

In May 2013, at the request of London Underground, the locomotive was painted in red London Transport livery (similar to that worn by the ex-GWR pannier tanks used by LT until 1971) and numbered L.150, to commemorate the 150th anniversary of the Metropolitan Line.

A small set of images showing GWR 4575 "Small Prairie" Class 2-6-2T Tank L150 in action on the Bluebell Railway whilst on hire from 5 July 2013. The engine left the railway to take part in the 150th Anniversary of the Hammersmith & City Line in August 2014.

The first Locomotives of the Great Western Railway (GWR) were specified by Isambard Kingdom Brunel, but Daniel Gooch was soon appointed as the railway's Locomotive Superintendent. He designed several different 7 ft 1⁄4 in (2,140 mm) broad gauge types for the growing railway, such as the Firefly and later Iron Duke Class.

The ex GWR Prairie 2-6-2T No. 5521 / London Transport No. L150, now has a new permanent home at the Gwili Railway at Bronwydd Arms, Carmarthenshire in South Wales.

2-6-2T GWR Prairie locomotive arrived on The Bluebell Railway in July 2013 in the London Transport red livery it wore for the 150th anniversary celebrations on the London underground, hence L150.

May 5, 2024 · Great Western Railway Prairie Tank locomotive, L150 (5521) in London Transport maroon livery running round at Ongar Station on the Epping Ongar Railway during their Festival of Steam Gala event...

To mark 150 years of the opening of the Metropolitan line (and thus the London Underground network) GWR "Prairie" tank 5521 was repainted into London Transport lined red and operated between Harrow/Watford/Uxbridge top and tailed with electric loco No12 'Sarah Siddons' and 20189 also repainted in LT red.