The Class 411 4-CEP was one of many electric multiple units that were the backbone of British Rail services in the South until the early 2000s. I don't think i ever travelled on one, well until yesterday. A preserved set is on the Chinnor & Prince Risborough Railway and yesterday a special Blue Electric Day was held with the EMU running services up and down the small preserved line.
The EMU was hauled by a diesel locomotive of course as the line didn't have electrified third rail but that did not matter as it was great to finally see and ride on a 4-CEP which i've always had a soft spot for and indeed when i started my N gauge BR model railway layout a 4-CEP was the first model i bought! You can see my photos here.