Hornby R40248 LNER Mk3 Slam Door TF Coach Number 41099 in LNER Red / Silver unbranded livery - OO Gauge

In-order to allow running at 125 mph on Britain's railways, new rolling stock was needed by British Railways in order to replace the aging Mk2s. Significant improvements included new secondary air suspension between the bogies and the coach body as well as aerodynamic skirting on the underframe. Mk3 Coaches are 75ft (23m) long, enabling far greater capacity than older coaches. Mk3 Coaches also incorporate disk brakes and wheel slip protection enabling faster deceleration.

The first Mk3 Coaches to be delivered were used as part of the HST prototype, along with the two Class 41 diesel power cars in 1972. Mk3 Coaches entered service in 1975 along with the Class 43 forming the iconic InterCity 125 trainset.

Following a period of privatised operations carried out by Virgin Trains East Coast, the InterCity East Coast franchise was re-nationalised. The new operator, named LNER in reference to operator of train services in the area between 1923 and 1948, is owned by the Department for Transport and currently awarded the franchise until at least 2025. LNER inherited a large fleet of IC 125 and IC 225 sets, but quickly began replacing the ageing stock with more modern Hitachi built high-speed multiple units. The last IC 125 train operated by LNER ran as part of a farewell tour at the end of 2019.