The RAF's new stealth jet is expected to be declared ready for combat in time to counter the “resurgent Russian threat”.

Gavin Williamson, the Defence Secretary, is thought to say today that the F-35B Lightning, the latest addition to the RAF’s fighter jet fleet, is capable of launching combat missions.

Details of what the ‘Initial Operating Capability’ (IOC) entails is expected to be announced by the Secretary of State later today at RAF Marham, Norfolk, the home to the F-35s and the Tornado, the RAF’s workhorse since the 1970s.

The Tornado will be retired from service in 2019 after four decades of active service, during which time it has provided critical air power in Iraq, Afghanistan, the Balkans and wider afield.

It is anticipated that Mr Williamson will also announce a significant enhancement to the RAF’s fleet of Typhoon fighter jets, a move welcomed by Defence experts.