Q22.22. HST Driving Van Trailers.

In the late 1980s a number of HST power cars were modified to act as Driving Van Trailers (DVT) on the ECML when the Cl. 91s entered service, as much of the MK IV stock was not immediately available. They could be easily identified as they were fitted with buffers. Once sufficient new stock was available these cars reverted to standard HST use. Each had retained its engine and so was capable of moving under its own power despite the DVT designation. For the resumption of use as an HST power car were any physical modifications required and are dates known for their return to power car status?  Were all cars that were fitted with buffers used as DVTs? (Paul Chancellor: 9408)