The Mk.3 DVT, Driving Van Trailer, was produced to allow shuttle type train working to be introduced on the West Coast mainline in the 1990s. The coach was equipped with a drivers cab to allow the driver to control a powerful electric locomotive at the rear of the train. This allows a train to be driven in either direction without needing to reposition the locomotive.
This detailed Dapol N gauge model of coach 82115 in it's recent heritage 'rail blue' livery (though to me it appears to be more teal blue than the BR monastral blue). This coach is owned by Data Acquisition & Testing Services and operated by the Rail Operations Group, often seen being used as a barrier coach when HST stock fitted with central buckeye couplers only needs to be moved in a train with a locomotive and other stock fitted with conventional side buffers.