For many years a number of summer Saturday London Liverpool St - Norwich services were extended to/from Great Yarmouth. The line between Norwich and Great Yarmouth is not electrified, requiring diesel haulage (normally a Class 47) over this section. The normal practice was to leave the electric loco which had hauled the train from London coupled to the coaching stock, with the 47 hauling the whole trainset, hence the use of the term 'Yarmouth Drag' for these services. On the Great Eastern Mainline the electric locos work in push pull mode with a driving van trailer, and the loco remains attached to its train during normal service. The loco is normally positioned at the London end of the train. Trains from London to Great Yarmouth reverse at Norwich, with the 47 and electric loco at the head of the train on the journey to the coast. At Great Yarmouth the 47 would run round the train, leaving the electric loco on the rear, and ready to return to London on arrival at Norwich.
This picture - which I think dates from the mid 1990s, shows an afternoon Great Yarmouth - London Liverpool St. service, with the Class 86 electric loco on the rear. The train has just passed Buckenham station. At this time Intercity services were formed of 86/2 locos and rakes of Mark II coaching stock, with the Mk1 buffet cars soldiering on (one of which is the third coach in the formation). It always seemed odd to see an 86 in the middle of the Norfolk countryside away from the wires and with its pantograph down.