Built in TT:120 scale, the GNER HST Mk3 Trailer First with running number 41170 is a superbly detailed model finished in GNER’s distinctive deep blue and red livery. Carefully applied branding, crisp detailing, and an accurately moulded interior capture the sophistication of the original design, recreating the spacious and comfortable seating arrangements seen within the original coaches. 
The GNER HST Mk3 TF 41170 pairs seamlessly with other TT:120 Mk3 coaches and power cars, bringing authenticity and prestige to any modern-era railway.
History
BR developed the Mark 3 in response to improved comfort provided by airline companies and the convenience provided by the family car, both of which were taking traffic away from the railways in the early 1970s. Originally conceived as locomotive-hauled stock, the first to be produced were for the prototype HST in 1972. The first production vehicles entered service in 1975 and continued to be built until 1988. 
Although outwardly similar to the Mark 2 carriage, it is of a completely different design, having a ridged roof and under-frame skirt, whereas its predecessor had a smooth roof and visible below-frame equipment. The body is 75ft-long (23m), which is 10ft (3m) longer than the Mk2. It is also of full monocoque construction (one piece body shell) with an all-welded mild steel, stressed skin.
To give it a superior smooth ride, it also has secondary air suspension and disk-brakes fitted to the wheels (rather than clasp brakes) which allow for running at speeds of up to 125mph (200km/h) and efficient deceleration. The Mk3 HST coaches differ from the Mk3A loco-hauled coaches mainly in terms of the electrical arrangements, but are otherwise much the same. 
These HST coaches take their supply from a three-phase electrical supply directly from an auxiliary alternator in the power car, whereas the Mk3A convert the single-phase AC supply from the locomotive through motor generator units under the floor, which change the train supply to three-phase.