More than 1.5 million journeys have been made in premium economy train carriages since the service was launched two years ago, operator Avanti West Coast said.
The company’s introduction of standard premium fares in May 2021 was the first times three classes of travel was offered on Britain’s domestic railway for decades.
The service is positioned between standard class and first class, meaning customers benefit from wider seats, more leg room and a guaranteed table, but do not receive complementary refreshments.
Thursdays are the busiest day of the week for standard premium, with leisure journeys being the most common reason for travel.
The ticket's popularity is a great example of why it's vitally important to innovate on the railways— Andy Mellors, Avanti West Coast
Upgrading from standard class costs from £15 between Birmingham and London, and from £30 between Glasgow and London.
Third class rail travel was abolished on domestic trains in Britain in 1956, and renamed second class before later being branded standard class.
Avanti West Coast managing director Andy Mellors said: “Standard premium is all about giving our customers extra choice, seven days a week.
“We’ve listened and the ticket’s popularity is a great example of why it’s vitally important to innovate on the railways.
“Coupled with £117 million investment to transform the interiors of our Pendolino fleet, we have to work harder than ever, deliver on our promises and give people more reasons to return to rail.”
The Government faced calls to nationalise Avanti West Coast services last year due to major disruption, but the operator was handed a six-month contract extension in March after its performance improved.
