Baku, May 2, AZERTAC

The UK is increasingly vulnerable to the threat of missiles and drones after decades of cost-saving cuts eroded its once world-class air defences, military sources and Cold War veterans have warned, Sky News reported.

Defence chiefs are understood to be exploring options to regrow Britain's ability to protect critical national infrastructure - like power stations, military bases and government buildings - from the kind of Russian cruise and ballistic missile strikes that are devastating Ukraine.

But any credible "integrated air and missile defence" plan will cost billions of pounds and would likely require a further increase in defence spending beyond a proposed rise to 2.5% of national income recently announced by the prime minister, according to defence sources.

"Can the UK defend its cities from the skies if there was a barrage of missiles? No," a senior defence source said, speaking on condition of anonymity.

"Do the public know what to do in the event of an air attack? No... Put simply, are we defended? No."

As part of a series called Prepared For War? Sky News visited air defence sites that once played a key role in protecting Britain during the Cold War - and spoke to veterans who were part of the force that had been on alert to respond to any Soviet air threat.

Flicking a line of switches to prime a simulated batch of missiles from inside a cabin at an old military-base-turned-museum in Norfolk, a former Royal Air Force technician watches a screen as a radar scans for enemy aircraft.

"It's picked up a target," says Robert Findlater, pointing at a dot on the monitor, which looks more like a retro computer game.

A beeping noise indicates the signal from the radar is becoming stronger as the hostile aircraft approaches.

Once in range, red letters on one of the screens that had read "hold fire" switch to the words "free to fire", written in green.

Mr Findlater leans forward and presses a big red button.

Suddenly there is a roar as the simulated noise of a missile blasting off shakes the cabin.

The Bloodhound air defence missile, powered with a Rolls Royce engine, could reach 60 miles per hour in a tenth of a second before rocketing up to twice the speed of sound as it powered towards an enemy aircraft or missile - state-of-the-art technology in its day.

"We've been successful in our launch," the RAF veteran says, with a smile.

He then peers back at the screen, watching a line of what looks like radio waves jumping up and down, until there is a spike to indicate the missile closing in on the target.

"It [the radar] is now looking for the missile, and there she is in the beam. Next thing you see - that's the warhead.

"It's gone off, and you killed it," the veteran says, finishing the simulation.

Long retired, Mr Findlater joined the RAF in 1968.

He rose up through the ranks to become chief technician on a Bloodhound unit, charged with ensuring the missiles were ready and able at all times to fire at any threat.

Stepping outside the cabin, from where the system was operated, to a patch of grass, the veteran showed Sky News around the actual weapon - a lethal-looking collection of rockets and warheads, painted white and lying horizontal now, rather than pointing towards the sky.

Asked what message it had been designed to send to NATO's former Warsaw Pact foes, Mr Findlater said with a chuckle: "Don't come knocking... It says we're ready for you."

The ground-based systems, which had been dotted around the UK's coastlines, used to be part of a layered grid of Cold War air defences that also included fighter jets and other weapons.

But the entire arsenal of Bloodhound air defence missiles was taken out of service after the Soviet Union collapsed in 1991, while air bases and fast jet squadrons were reduced to save money as successive prime ministers took what has been described as a "peace dividend".