The electrification of the East Coast Mainline occurring in 1987 was almost complete, with deliveries of new electric Class 91s occurring when British Rail realised the Mk4 coaches and Mk4 DVT were still not ready to go into service.

As a result, eight eastern region HST power cars were converted to operate as surrogate DVTs in tandem with the new electric locomotives and a rake of Mk3 coaches. The conversion process involved the fitting of buffers and remote-control equipment.