The Russian aircraft carrier fleet has abandoned its flight training mission and moved into the North Sea, the UK Ministry of Defence has confirmed.
The eight-strong flotilla, led by the Admiral Kuzentsov, is been tracked by the HMS Richmond and several NATO vessels. The Russian media has dubbed the mission 'Operation Sea Fist'.
A spokesman said: "It is pretty unambiguous that they have set a course to pass through the Dover Strait."
Vladimir Putin has already tried to divide the Royal Navy's efforts to track his fleet by recalling two corvettes from the Mediterranean forcing the HMS Dragon to head south from Portsmouth to intercept.
It is understood there is also a Dutch submarine operating south of the English Channel.
A Norwegian navy frigate has also been following the Russian flotilla, which is being kept under close watch by a P-3 Orion.
Two further British warships are currently steaming up the east coast to intercept the Russian fleet after the Kremlin boasted they are "seizing control" of the Mediterranean.
Type-45 destroyer HMS Duncan - the world's most advanced air-defence destroyer - sailed from Portsmouth last night to join frigate HMS Richmond, which has intercepted the Kuznetsov task group of eight ships.
The HMS Richmond has taken up station a few hundreds yards from the task force. It will remain as an escort while the Russians remain in an area of UK national interest.
In a sign of the escalating tensions with Russia, UK Defence Secretary Michael Fallon today warned Moscow: "When these ships near our waters we will man-mark them every step of the way. We will be watching as part of our steadfast commitment to keep Britain safe."
According to the Ministry of Defence: "Shadowing ships is regular business for the UK Royal Navy, supported on this occasion by Royal Air Force surveillance aircraft.
"They will continue to escort the Russian Task Group and provide a visible presence south through the North Sea and English Channel as the ships conduct their passage and carries out flying operations."
The UK is working alongside NATO partners to monitor the warships passing the UK this week.
It marks a further breakdown of relations between the two countries after after Foreign Secretary Boris Johnson became embroiled in a row with the Russian embassy last week.
Johnson called on people to demonstrate outside Russia's London embassy last week in protest against Russia's bombing campaign in the Syrian city of Aleppo.
But Moscow responded by branding his call for protests "shameful" and accused him of "Russophobic hysteria".
Britain's mobilisation of the aircraft carrier fleet off the coast of Scotland is the latest in an increasing presence of international naval assets in the area.
After completing training it is understood the aircraft carrier fleet will head to an anchorage on the Moray Firth where it will be refuelled before continuing to the Mediterranean.
Naval assets from Norway, Sweden, Finland and the Netherlands are all believed to be on standby.
As well as the Royal Navy, the Royal Norwegian Navy, Finnish Navy and Royal Netherlands Navy have vessels surrounding the North Sea.
NATO aircraft are also patrolling the area, with tanker aircraft on station ready to refuel any fighter jets tasked with observing the Russian fleet.
Russian military expert Alexander Khrolenko said: "While the North Atlantic bloc is stalling in the sands of the Middle East, the Russian Navy seizes control over the Atlantic, not to mention the Mediterranean and Black Seas."
He added: "They [NATO] have no equal in the Mediterranean."
In addition the RAF Quick Reaction Alert squadrons in RAF Lossiemouth in north east Scotland and RAF Coningsby in Lincolnshire have been ordered to remain on standby in case they need to intercept any Russian jets straying into UK air space.
The Admiral Kuznetsov is protected by a battle cruiser and a pair of large anti-submarine ships.
It is also protected from below the surface by an attack submarine.
The Kuznetsov has undergone an extensive refit since its last deployment to the Mediterranean in 2014 when it had to be followed by several tugs in case its steam turbine engines packed up.
Earlier this week the Norwegian navy followed the heavily-armed fleet as it sailed south from Severomorsk, near Murmansk in the Barents Sea.
According to the Ministry of Defence, the Russian fleet is being kept under close observation by the Royal Navy and the RAF.
A source told MailOnline: "The Admiral Kuznetsov is currently conducting flight operations off the east coast of the Orkneys.
"The pilots need to be certified for carrier take-offs and landings at day and night before it takes up station in the Mediterranean.
"They are free to do this in international waters, but once they are in the English Channel, the aircraft will be grounded."
The MOD confirmed the Royal Navy would shadow the carrier and its fleet while it remains in the UK's area of interest.
Also, RAF Typhoons and Tornadoes are on red alert at airbases in Lossiemouth in North East Scotland and Coningsby in Lincolnshire in case any Russian jets stray into UK airspace
The fleet could possibly route around Ireland's west coast to avoid the English Channel, although there is far greater shelter avoiding the Atlantic Ocean.
However, after going through the Bay of Biscay and down the Portuguese coast, the fleet will pass through the nine mile wide Gibraltar straits before reaching its area of operation.
It is understood the fleet will resupply before continuing to the Mediterranean.
The Admiral Kuznetsov is the Russian flagship and the country's only aircraft carrier.
The French already have the Charles De Gaulle operating in the eastern Mediterranean.
Major Elisabeth Eikeland, spokeswoman for the Norwegian Army's National Joint Headquarters said: "We have been informed that they are en route to the Mediterranean.
It's not every day that so many ships sail together off Norway."
According to the Russian Ministry of Defence, the aircraft carrier taskforce departed on Saturday to the Mediterranean.
A spokesman said: "The group consists of the aircraft-carrying heavy cruiser Admiral Kuznetsov, the Pyotr Velikiy battlecruiser, large anti-submarine ships Severomorsk and Vice-Admiral Kulakov and support vessels."
The Russian MOD claimed: "Special focus will be made on safeguarding security of maritime traffic and other types of maritime economic activity of Russia and also on responding to the new kinds of modern threats such as piracy and international terrorism."
The Admiral Kuznetsov had previously operated in the Mediterranean early in 2014.
8,500 nautical miles
1,690 plus 626 in the air group.
12x SU-33 fighters
'Putin readies for war'
Vladimir Putin is readying for war, warns one of his former Russian KGB comrades.
Former Soviet secret services boss Gennady Gudkov told MailOnline said: "If anyone still does not understand which direction the situation in Russia is heading, I can tell you. The country is being prepared for a military conflict."
Colonel Gudkov, 60, said: "There are lots of signs of militarisation in Russia.
"A bloated military and defence budget, quick rearmament of the army, almost monthly army exercises and tests of the newest samples of dreadful hardware."
Gudkov said Putin is working behind the scenes in readiness for conflict, adding: "There are active renovations in bomb proof shelters, purchase of gas masks and defence kits for civilians, along with a massive mobilisation in many places.
"Military (naval) activities in the Middle East, in the Black and Mediterranean seas, plans to resume and enhance military bases aboard.
"Growing military propaganda, spy madness and the search for internal enemies - all are typical of a pre-war situation.
"Laws have been adopted that allow the use of military force abroad, and hide information about losses."
Comparing the mood to the Stalin era ahead of the Second World War which initially saw the USSR in a pact with Hitler before ensuring his eastern flank defeat, he warned: "The country went through the same things in the 1930s.
"And the results are known, too."
Gudkov, an MP until he was forced out by the Kremlin in 2012, claims that last month's parliamentary elections, comfortably won by former KGB spy Putin's allies against a weak and emasculated opposition, signalled a transition in Moscow.
"It is entirely clear that the country has switched from authoritarian to totalitarian," he said.