Russia has threatened to use nuclear weapons against the UK (Image: Getty)

“London-Washington contacts take place, and possibly also London-Paris. NATO information-sharing begins. Within 10 minutes after the attack, the authorities must transmit an air-raid warning or emergency alerts via television and radio broadcasting, the internet and other Government channels.”

Dr. Starchak noted that in any scenario, three to five minutes will be spent on assessing the event, calculating the trajectory and transmitting information to the political leadership. The remaining time will be spent on decision-making.

RAF Fylingdales would detect the Russian missile (Image: Getty)

“If yes, then an order must be given in encrypted form to the SSBN Vanguard commander to launch. On the submarine, in addition to the commander, one other officer must confirm readiness for a retaliatory strike. The submarine prepares the launch and carries out the retaliatory strike with SLBM Trident II D5.”

Russia has Oreshnik missiles in its arsenal (Image: Getty)

Regarding whether Moscow could launch an attack, the expert said it could occur if Kaliningrad — a Russian province inside Europe — were blockaded or cut off, “in which UK involvement would be clearly and undoubtedly evident”. Another reason could be British “participation in a direct military clash between NATO and Russia in which Russia suffers substantial setbacks”.

Dr. Starchak also suggested that a strike could happen “during a military clash between NATO and Russia, when the UK strikes Russian strategic military facilities, which Moscow interprets as an attempt to deprive it of the ability to use nuclear weapons”, as “a response to a UK or joint Western nuclear strike”, or as a scenario “in which Moscow mistakenly takes certain UK or joint NATO actions as preparations for a disarming strike against Russia”.

Finally, a nuclear attack could come if as a result of the UK “transferring nuclear technologies or components for a ‘bomb’ to Ukraine“. But the specialist mentioned that Russia’s “first target would probably be Ukraine itself, as a safer option”.

Emeritus professor at the University of Buckingham, Anthony Glees, does not believe a nuclear attack on the UK by the Russia is “at all likely”, even though Britain is “already in a limited war with Russia”.

He said: “We choose to call it a ‘hybrid’ war, or a ‘grey-zone’ war but the successful Cold War doctrine, one Russian foot over the border with a NATO state means Russia will be obliterated’ has been ditched. Now we put up with Russian footprints all over the UK and all over the states that are our European NATO allies. I am convinced Putin is testing and probing what he regards as this key weakness on our part and that the coming war with him, unless we can deter him, will be fought ‘conventionally’, that is, without nuclear weapons but with drones, with subversive tools of all kinds, and ultimately with Russian troops. As I’ve said more than once, it is my thought that a Russian attack on the UK will come either via the Baltic Sea, in which case the UK will be at the end of a chain, or ‘over the top’ via the High North in which case Norway and the UK will be in prime pole position.”

There are three reasons why Putin would target the UK with nukes “only as a very last, suicidal ‘bunker’ response to a war with us”, Prof. Glees added. “He wants Britain and indeed all of Western Europe to be Russian colonies,” the specialist said. “A nuclear attack on the UK would destroy the UK for all foreseeable time, France and Western Europe along with ourselves, and so be worthless in asset terms. We would be turned to radioactive ash but so would our wealth.

“Secondly, the prevailing wind blows from the west towards the east. A UK destroyed by nuclear weapons would produce a radioactive wind, possibly a blizzard, that would inevitably make its way towards the European part of Russia. Putin might be safe in his Black Sea fun palace but his allegedly beloved Russians would fall sick with radiation disease and end up dead.

“And third, if we knew we were under attack from Russia and that attack proved to be nuclear, the Prime Minister’s orders to our Vanguard continuous at sea submarine force would be clear and devastating for Russia. The order would go out to launch our nuclear ballistic Trident missiles from our nuclear powered submarines and turn the Russian Federation into ash.”

On what he thinks would happen if the Kremlin did launch a nuclear weapon, Prof. Glees said: “Putin knows what we all know: Britain has no way of preventing a ballistic nuclear tipped missile (‘ballistic’ means it can be launched from anywhere on earth or from space, so travels in space, outside Earth’s atmosphere, before entering it to hit its target). He also knows that we have no way of preventing the UK from being attacked by a cruise missile which travels low and can evade our electronic early warning station based at RAF Fylingdales which uses space surveillance to try to detect a ballistic missile but is of no use at all in detecting the Russian Burevestnik or Storm Petrel cruise missile, for which our codename is Skyfall, once flying low over the central European plain towards the UK.

“We think it is still being developed but once ready for use its range is unlimited. Of course, Russia has other nuclear weapons it could use but in my view Skyfall would be Putin’s weapon of choice. It is subsonic, however, and travels at 580 mph so could potentially be spotted by land-based radar although with difficulty.

“There might just be enough time for the Prime Minister to order the captain of whichever Vanguard sub was at sea to retaliate against the Russians and Russia would be obliterated. Margaret Thatcher insisted this weapon should be a doomsday weapon and take out every city and major town in Russia, and we think this is still the case.

“If Skyfall were used we might have a few more minutes to prepare but the difference to ordinary Brits would be marginal. Five minutes to seek a safe space, no more than that. Those five minutes would actually be used to say ‘goodbye’ to our loved ones and pets. Then it would be over.

“Whilst in theory Putin might decide to target London and nowhere else, that might mean that other parts of the UK would have longer to prepare themselves perhaps up to half an hour. But it is unlikely that Putin would do this. Three or four Skyfalls, one at London, one at RAF Fylingdales and one at our nuclear bases on the Clyde, so Scotland, would end the matter, in his favour.”