The South Shields trolleybus system was inaugurated on 12 October 1936 when four Karrier E4 trolleybuses with Weymann H56R bodywork entered service between Market Place and Freemantle Road. The trolleybus service proved extremely popular and a further four similar vehicles were purchased in 1937 to replace trams on the Stanhope Road service. The only difference was that the second batch of vehicles had one less seat on the upper deck than the original four.
204 entered service on 30 April 1937. In 1950 a route number box was provided alongside the front ultimate destination indicator, ready for the introduction of route numbers. Other than that, 204 had a remarkably uneventful 26 years in service.
The Reading Transport Society had made enquiries regarding the purchase of 200 for preservation. The South Shields Transport Committee agreed to make a gift of the vehicle to the Society. Unfortunately, 200 was damaged in an accident inside Chichester depot and 204, withdrawn in February 1963, was provided as a substitute vehicle.
204 was kept in outside storage in Reading during the early years. On its arrival in Reading, on 31 March 1963 it was taken to Chiltern Queens depot in Woodcote where some restoration work was carried out. In June 1965, 204 was moved to Smiths Coaches garage in Reading where it received an external repaint.
Over the August bank holiday weekend in 1966, 204 was taken to the Reading Show at Kings Meadow and used as an RTS sales stand whilst also involving members trying to canvas support from the public to save the Reading trolleybus system.
In July 1967, 204 was moved to accommodation at Theale where it remained until 6 June 1970, when finally, 204 was transported to the Trolleybus Museum at Sandtoft. It remained in outside storage until the third depot at Sandtoft was constructed in March 1973. By this time, the bodywork had become very fragile having mostly being accommodated outside for 10 years. 204 had to wait its turn until finance was available to carry out a thorough restoration.
A costly major body rebuild commenced in 2001 and a thoroughly professional job was carried out at Sandtoft by a team led by Brian Maguire. Much of the money to finance the rebuild came from the BTS membership following several appeals.
In May 2005, 204 entered service at Sandtoft looking magnificent. 204 is the only Karrier E4 and, also, the only South Shields trolleybus in preservation.
On 1 April 2006, 204 visited its hometown to take part in South Shields transport centenary celebrations and was put on display in Dean Road depot.
204 continues to operate at the Trolleybus Museum at Sandtoft at regular intervals and is in good condition for her age.