The company is embarking on a redesign and rebuild all 302 carriages in its electric 225 fleet.

The project is the largest of its type in the UK and GNER's biggest single investment since it started running services on the East Coast Main Line.

Interior features include softer, contoured seats with improved back support and fold-up arm-rests for easier access.

GNER chief executive Christopher Garnett said: "After more than a decade of service, the train interiors needed a total transformation.

"Under the rebuild, as well as ensuring that the insides of the trains look and feel fantastic, a huge effort has gone into making sure that everything, from the toilet doors to the kitchen ovens, actually works as it should."

All of GNER's Mark 4 coaches will be rebuilt to the new design standard at Bombardier's Wakefield site, before entering passenger service on a rolling basis from September.