The possibility of using electricity and 'Kitson type' trams was considered during the planning of the Wisbech and Upwell line, but it was eventually decided to build steam trams. The GER's Locomotive Superintendent, T.W. Worsdell, designed these small vertical boiler locomotives to meet this need. They had a distinctive wooden body resembling a goods brake van. To meet the requirements of the Board of Trade Railway Inspectorate, they were fitted with cowcatchers, side skirts, condensing apparatus, spark arrestors, automatic governors, and warning bells. They were also designed with controls at both ends, and sliding windows on the sides, front, and rear.

Ten of these GER Class G15 locomotives were built between 1883 and 1897. When rebuilt in the early 20th Century, they were fitted with the same 140psi boilers used on the newer J70s. The last G15 / Y6 was withdrawn in 1952, and survived at the Stratford paint shop for about a year before being cut up.  These locos are not what livvy is based on, these were just the beginning of the type of loco.

With increasing traffic in the early 20th Century, James Holden designed a more powerful 0-6-0 version of the Class G15 locomotives. Visually these were very similar, but boasted outside cylinders with Walschaerts valve gear, and a 140psi boiler. This compared to the Y6's 120psi boiler and inside cylinders with Stephenson valve gear.

A total of twelve were built between 1903 and 1921, for use on the Wisbech & Upwell and a number of dock railways. With the arrival of the new Drewry diesel shunters, the last scheduled steam service on the tram line was in 1952, but No. 68222 stayed until March 1953 as a backup. The last four J70 was withdrawn from the British Railways system in 1955.  these locos are what livvy is based on.