On standby 24/7, the RAF's Typhoon crews remain the closest the UK has come to a direct confrontation with Russia's military machine.
The Quick Reaction Alert (QRA) squadrons are ready to scramble within minutes to uninvited 'Bears' and other rogue aircraft in or near UK airspace.
Flying the Typhoon FGR.Mk 4, a multi-role combat aircraft, pilots are faced with potential threats ranging from Russian bombers to hijacked airliners.
The heavily armed interceptors have flown close enough to wave to their Russian counterparts - who have been known to engage in brinkmanship.
Former RAF fast jet pilot Justin Hughes, who served on the QRA at Leuchars Station on the east coast of Scotland and in the Falklands, said: 'The aim of the QRA is to protect the integrity of the UK's territorial airspace and beyond in cooperation with other Nato countries.
'All civil and military aircraft fly with a transponder, which pushes out a signal to identify it to air traffic control.
'If anything comes into UK airspace that cannot be identified or there is another type of problem then potentially that is a threat to the integrity of UK airspace, so the controllers will launch a QRA to intercept it.
'The idea is that the jets are launched within 10 minutes of a hooter being sounded, at which point the pilots run to their aircraft and scramble as quickly as possible. In an ideal world there will be some kind of notice first, with the pilots going into what's called cockpit readiness.'
The QRA was called into action on April 30 this year when two Typhoons based at RAF Lossiemouth in north-east Scotland intercepted a Russian Tu-142 Maritime Patrol aircraft, codenamed Bear-F by Nato.
Two days later another launch in response to a civilian aircraft which was not responding was resolved when communications were reestablished, with the plane landing safely.
The alerts followed launches in response to Russian aircraft on two days in 2022 and on four in 2021, according to the Ministry of Defence.
The figures disclosed to Metro.co.uk also show there were six days of launches in response to unspecified aircraft in 2021, four in 2022 and one to the same point in 2023.
The falling number of alerts in response to Russian jets - with the latest known incident and one in August involving patrol aircraft rather than bombers - may reflect how the Kremlin's resources have been degraded by its catastrophic full-scale invasion of Ukraine.
Dating to the Cold War era, the Bear aircraft were detected by an integrated early warning system which draws on radar and civilian and intelligence agencies to identify possible threats.
Once an alert is confirmed, crews are scrambled at Lossiemouth, with pilots at RAF Coningsby in Lincolnshire, the second QRA base, put at cockpit readiness in their Typhoons.
After the pilots have raced to their aircraft and launched, with the capacity to go supersonic, the aim is to intercept the aircraft and escort them out of the UK's area of interest.
Typhoon detachments also operate in the Falklands, Estonia and Cyprus.
'To some extent it's just a job you are trained to do and it becomes fairly routine to get the flight kit on and run out to the aircraft to get going,' Hughes said.
'It got a bit more interesting in the Falklands when I was launched against an unidentified aircraft from Argentina with no warning.
'I was woken up in the morning by the hooter going off to be airborne within 10 minutes, which was a bit more disorientating and challenging.
'But this is just an extreme example of the job you are trained to a high degree to do. The Bears I was launched to intercept turned back or diverted before we got near but another incident that stands out is when I was launched for a potentially hijacked aircraft over the Atlantic which we escorted back into Scotland.'
Typhoons intercept two 'Bear-F' aircraft in the North Sea and escort them out of the UK area of interest
Typhoons launch from Lossiemouth and Coningsby in response to Russian TU-160 Blackjack bombers
RAF Typhoon jets intercept the Russian military aircraft north of Scotland
RAF jets from Coningsby launch to an unresponsive aircraft before communications are reestablished and it lands safely
The supersonic Eurofighter Typhoon has a top speed of Mach 1.8 (1,380mph) and is armed with radar-guided, air-to-air missiles and an internal 27mm Mauser cannon.
Hughes flew the predecessor jet, the Tornado F3, during his time on the QRA between 1993 and 2000.
'How fast you fly depends on the nature of the threat,' he said.
'For example if it's a Bear 300 miles out you would fly at around 450 knots (517mph), which is normal operating speed. If it is a more urgent threat this might create the sonic booms that are sometimes reported over the UK.
'As to why the Russians continually probe our airspace, one of the most likely explanations is that they are gathering intelligence, perhaps at a time when we and our allies are doing a big military exercise.
'Another is that they are testing our readiness to see when the interception occurs and how far out.'
Phil Keeble, another former fast jet pilot, was posted to the QRA between 1982 and 1984 during a 28-year RAF career.
The former Phantom F4 and Tornado F3 pilot, who served with the northern QRA while it was based at RAF Leuchars on the east coast of Scotland, was involved in some tense encounters with Russian aircraft.
'You identify them from a distance and slowly come up behind them from about three or four miles away and pitch up at the port side normally,' Keeble said. 'You're well spaced out so it's very safe and you take photographs of them and often you give one another a little wave, which might sound a bit pathetic but you are showing you recognise their professionalism and vice versa. Hopefully they turn away and you swap sides to the right and follow them gently out of our airspace.
'It helps to have a number two with you sitting well back within missile range in case there is any nonsense but that is more of a war-time scenario.
'Sometimes they wouldn't play ball and they would slow down and try and stall us, or they would turn into you without warning, which could be a bit hairy. Another manoeuvre was to descend through cloud, in which case you would track them on radar before they came out below. They could also turn out to sea trying to get you to get crash, which wasn't very sporting, and other times they would shine searchlights in your eyes.'
Aside from their intelligence-gathering role, rogue aircraft represent a hazard to commercial air traffic as they often do not talk to air traffic controllers or 'squawk' codes identifying their presence.
On longer encounters, the Typhoons are refuelled in mid-air by an RAF Voyager from Brize Norton in Oxfordshire, with a Handley Page Victor aircraft fulfilling the role during Keeble's QRA service.
'There could be long intercepts of up to five or six hours with air-to-air refuelling from a Victor tanker,' Keeble said.
'You had to keep alert and be sensible, firm and not provocative.
'By the time you got back you'd be absolutely shattered and it could be nerve-wracking, but you didn't have time to stop and think about it, you just got on with what you were trained to do.'
Air-to-air refuelling was required in the latest known scramble involving a Russian jet, with Typhoons intercepting the Bear off the coast of Scotland.
Norwegian F-35A fighter aircraft were also involved in the response to the reconnaissance and surveillance aircraft, which did not enter UK airspace.
Another QRA launch took place on November 12 last year in response to two Russian TU-160 'Blackjack' bombers, capable of going supersonic, as part of the same 'handover' system among Nato countries.
Both pilots agree that Moscow aims to use the continued probing to gather intelligence about the allies' defence capabilities.
But Keeble also detects an element of grandstanding.
'As to why they keep probing our airspace, a lot of it comes down to them telling us they are here and they are in charge, to which we say "move along",' he said.
'A lot of them had spy equipment onboard to assess our resources, such as how many aircraft we had and what frequencies and radar we were using.
'They were trying to pick up bits of intelligence they could use in case there was a war. At one point we had 14 aircraft airborne during a big Russian push to test our defences.
'We had guys flying in and out as part of a huge rolling machine.
'It was one hell of a day.
'Looking back, the QRA could be fun even if it could get what I would describe as exciting at times.'
As the discussion continues about the UK and other Western allies supplying modern aircraft to Ukraine, the Typhoon squadrons already have close quarters experience of Kremlin tactics.
Photographs from July 2019 show a Typhoon from Amari Air Base in Estonia flying in close proximity to a Russian IL-76 military transport aircraft detected close to the Nato member's airspace.
The images are a reminder of how close the pilots have come to Vladimir Putin's forces at a time when British tanks and other military kit is being deployed on the battlefield by Ukrainian forces.
Since becoming mission lead for Nato's Quick Reaction Force in the alliance's Baltic Air Policing operation, Typhoon airmen have been standing by for 'zombies', as they call suspicious Russian aircraft. The RAF's IX (B) Squadron, which is currently in high readiness at the Amari base, took over as the point force from their German counterparts in April.
Wing Cdr Scott Maccoll told the BBC that the rules of engagement were 'classified' but reiterated that 'our role here is to protect Nato airspace'.
A spokesperson for the MoD said: 'The primary role of the Royal Air Force is to defend the UK and when necessary, UK interests overseas.
'Today and every day, just as during the Battle of Britain, RAF aircraft and crews are held at continuous high readiness 24/7, so that they can take off within minutes to protect UK and Nato sovereign airspace.
'In the UK, the Falklands and currently Estonia the RAF hold a continuous ground readiness posture. Armed Typhoon fighter aircraft are available at each base all day every day allowing us to provide a rapid response to any possible incident or threat.'
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