The tram engines were built for the Wisbech and Upwell Tramway line in fenland Cambridgeshire, mainly to pull frieght wagons carrying fruit and vegetables to small towns; and part of the pre-grouping Great Eastern Railway. Due to legislation introduced in the 19th century steam engines that ran on or alongside public roads in Great britain had to have skirts or side plates that hid their running gear and be able to consume their own smoke. This was so as not to frighten horses pulling other vehicles on the road. In addition, many of the shunting manoeuvres outside Outwell depot yard had to happen on the streets, thanks to the very cramped yard conditions, which increased risks of hazards to the villagers and horses.
The design that characterised the J70's and Y6's was the fact that they had two cabs at either end of the locomotive, this not only improved visibility for the driver's operating the steam trams. This also reduced the risks of accidents along the roadsides and cramped quaysides of East Anglia's most important and largest ports. The tramway unlike many went through a dieselisation period, this saw the addition of the BR class 04 to the tramway fleet. However these diesel shunters only had one cab on the whole locomotive and thus has a more obscured view, they also had warning hazard (wasp) stripes on the backs of the cabs for increased visibility to pedestrians.
Most tram engines in Great Britain were introduced to pull large double decked passenger trailers on street passenger tramways. However the Wisbech and Upwell tramway used their own unique stock the characterised the line so. These carriages were designed with balconies at either end, with small step ladders on each side to reach the ground. This was necessary, because some stations along the tramway had no platforms, with only old shed's and carriages acting as a form of shelter. But a few lines, such as this carried freight as well and J70's were introduced to pull freight on roadside railways that were built under tramway legislation. The Wisbeech and Upwell tramway was known for pulling goods trains along the line (as mentioned earlier), the goods trains mostly consisted of strawberries from the strawberry season trains.
The line survived nationalisation and the steam trams worked it in British Railways colours until 1952, despite some of them being withdrawn as early as 1949. However some did manage to survive into the 1950's on the harbour quaysides of Great Yarmouth and Ipswich, but by 1956 the whole class was scrapped. The tramway lost most of its passenger traffic since the late 1920's, due to roadway competition, especially since busses were becoming more common and more people could begin to afford cars. Such was the common fate for almost all tram networks across the British Isles.
Toby the Tram Engine is based on the J70 engine. He first met Sir Topham Hatt while he was on holiday. At this point, trucks and buses had taken over his old tramway. At first, Toby was offended when Sir Topham Hatt's granddaughter called him "electric", but after being complimented, he felt better. When his railway closed, Sir Topham Hatt bought him to solve an argument with a policeman who was complaining that Thomas didn't have cow catchers or side plates. With Toby, the problem was solved.
In both the books and TV series, he is painted brown with a brass bell. He is the number 7 engine on the railway and has a coach named Henrietta and a baggage car named Elsie (the latter never appeared in the books or television series, only being mentioned in "The Island of Sodor: Its People, History, and Railways", but is very popular in fanfictions). In the books, he later obtained blue side plates, but in the TV series, he always had gray side plates.