The South West Trains (SWT) suburban line will definitely not come under public control in the next seven years after the Government announced it would be run jointly by a private firm and a Hong Kong state-owned operator.

Mayor of London Sadiq Khan had sought to incorporate all suburban services in the capital into London Overground but today the Department for Transport (DfT) said this would not be the case for SWT.

In the run-up to the Mayoral election, the former Labour MP said devolving the suburban lines to the public sector was a "top prioiry".

The franchise was instead awarded to transport giant First Group and MTR, which runs the Hong Kong metro service and is majority-owned by the country’s government.

A DfT spokesman said: “The (SWT) franchise was awarded for the next seven years. It’s safe to say it won’t be run by Transport for London (TfL) until the competition is open again.

“The winner has been announced. We are not trying to fob (TfL) off but we looked at all the business cases and the one we picked will be better delivered, have better capacity, they will have newer trains and they will have Wifi.

“TfL wasn’t the winner.”

From January 2016: Transport for London announce takeover of London's suburban rail services

In December Transport Secretary Chris Grayling rejected Mr Khan’s bid to take over the Southeastern commuter route, saying the proposed nationalisation would be the “biggest operating change on this railway since the 1920s”.

But in a letter to then-Conservative Mayor Boris Johnson, which was leaked to the Evening Standard, Mr Grayling expressed a desire to keep suburban rail lines “out of the clutches of any future Labour Mayor”.

A spokesperson for the Mayor of London said: "Sadiq continues to make the case for rail devolution as the only sensible long-term solution, but hopes the new franchise-owners can provide the level of service that Londoners and commuters deserve."

On today’s announcement, Mr Grayling said it was more "great news" for rail passengers following the recent announcement of a consultation on the Southeastern franchise.

He said: "First MTR South Western Trains Limited will deliver the improvements that people tell us they want right across the South Western franchise area, from Bristol and Exeter, to Southampton and Portsmouth, to Reading, Windsor and London.

"We are delivering the biggest rail modernisation programme for over a century and this franchise will deliver real changes for passengers, who can look forward to modern trains, faster journeys and a more reliable service."

From December: Chris Grayling blocked TfL takeover to keep commuter train routes out of Labour London Mayor Sadiq Khan's 'clutches', leaked letter suggests

The Government said the new operators will oversee a £1.2billion investment to improve journeys for millions of train passengers.

The new franchise claims it will provide 22,000 extra seats into London Waterloo each morning peak and 30,000 extra seats each evening peak, as well as a fleet of 90 new trains, providing more space for passengers on Reading, Windsor and London routes.

It also said there will be more frequent and additional services across the franchise, faster journeys across the network and earlier and later trains.

But Mick Cash, the general secretary of the Rail, Maritime and Transport (RMT), said the Hong Kong company is set to “make a killing at the British taxpayers’ expense”.