When it comes to railways I'm definitely a steam person. In fact I've yet to find a diesel or electric locomotive that inspires me in any fashion. Having said that I am, however, also interested in the history of the line that runs along the bottom of the garden and so I'll make an exception for the EM1. The EM1, which stands for Electric Mixed-Traffic 1, was specifically designed and built for the Woodhead line. They were powered from 1.5 kV DC overhead catenary and employed regenerative breaking to actually feed power back into the system when running downhill. They were predominately used for working freight trains through Penistone as this photo from 1955 shows.
The photo shows number 26020 which coincidentally is the only preserved member of the class and which I photographed at the National Railway Museum when I visited for The Great Gathering.
If you want more details on the EM1 then Wikipedia has a fairly informative page, and if you fancy one in model form then Heljan produce an OO gauge model exclusively for Olivia's Trains.