Virgin Trains said it would convert some of its first-class carriages into standard seating to increase capacity after signing a deal with the Department for Transport (DfT) to operate the franchise until March 2017.
The alterations will affect all 21 of Virgin's nine-car Pendolino trains, with one first-class carriage in each converted into standard seating by September next year. The move will create an additional 2100 seats per day on the route, which connects Glasgow Central with London Euston.
Meanwhile, all 76 of Virgin's Pendolino and Super Voyager trains will also be equipped with superfast wi-fi in the UK's first major intercity deployment of 4G technology on the rail network.
Virgin will also invest more than £20 million to modernise stations with extra staff and ticket machines, improved waiting rooms and more passenger help points. The deal comes as the operator prepares to open its new first-class lounge at Glasgow Central on Monday.
The new franchise will generate at least £430m for taxpayers over its 33-month term, which begins on Sunday.
It marks the end of a two-year period during which Virgin has run the franchise on a management basis, which precluded it from investing in new initiatives.
The arrangement followed a disastrous franchising process in 2012 that saw the DfT award FirstGroup the contract to run the West Coast Main Line, before scrapping the decision following a legal challenge from Virgin. A subsequent inquiry found that the DfT's handling of the process was "littered with errors". The fiasco cost taxpayers about £50m.
Patrick McCall, Virgin Trains executive co-chairman, said: "We're delighted to have reached a deal after some tough negotiations with the DfT. It puts the problems of 2012 firmly behind us.
"This deal is great news for passengers and taxpayers, with significant benefits for our customers as well as a big increase in the money we pay to government. We know wi-fi is high on our customers' priorities and we're delighted that we're going to be able to offer them free and super-fast wi-fi."