DESTROYING an "invincible" Challenger 2 in Ukraine was a stroke of pure dumb luck for the Russians, an ex-British tank commander said.
Colonel Hamish de Bretton-Gordon said it's the first time the world-beating tank has ever been damaged by enemy fire in combat.
Battlefield footage showed the wreck of a tank billowing smoke and flames near bomb-blitzed Robotyne, the focus of Ukraine's counter-offensive.
Defence sources confirmed the tank had been destroyed - known as a "K-Kill" – in fierce frontline fighting, but it is not yet what wiped the mighty vehicle out.
Former British officer Mr de Bretton-Gordon suggested the tank was either hit by a drone or blasted by a mine during intense fighting.
But he said it's unlikely the Russians would have known what type of tank they were targeting amid the heavy fighting on the frontlines.
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"It would be very difficult for the Russians to differentiate between Challengers, Leopards, T-72s, T-80s," Mr de Bretton-Gordon told The Sun.
"We know how dense the defensive lines are - the trenches, the minefields, how many thousands of Russian troops we've got there defending it.
"The fact that one tank has been hit and the world's talking about is pretty extraordinary. Challenger 2s have been around for 20 years and this is the first time one has been hit in action.
"This is a British tank that has been taken out by some sort of Russian fire and it was designed to fight the Russians, and that's what it's doing.
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"A tank that I spent many thousands of hours in - seeing it on fire and damaged is hard, it's tricky. But let's hope the protection did its business."
Fighting in the south has been intense, with ferocious Ukrainian troops storming Russia's frontline as their counter-offensive gathers pace.
The Ukrainian footage was filmed from inside a vehicle with a cracked windscreen as it drove past the wrecked tank.
Black smoke and flames are seen pouring from the Challenger 2, which was positioned next to a road with its barrel at right angles to the tracks, as if ready to fire.
The only other time a Challenger 2 had been destroyed in battle was by friendly fire in Iraq in 2003.
Two British soldiers were killed and two others seriously wounded when another Challenger 2 opened fire in darkness.
But despite the tank being wiped out in Ukraine, the machine's survivability was highlighted as it shows the turret still attached to the hull.
Challenger 2s have been around for 20 years and this is the first time one has been hit in action
Hamish de Bretton-Gordon
Usually when tanks are blasted, the explode and parts such as the turret fly off.
Mr de Bretton-Gordon said the Challenger 2 is designed to take a lot of damage - and believes it could be recoverable.
"Apart from the smoke coming out of the turret, there doesn't look like a lot of damage to me," he said.
"I would be very surprised if it's a complete write off. The fact the hatches are open would suggest to me the crew have got out.
"The Challenger 2 is very well protected and this would be the first to be damaged by enemy fire.
"The one in 2003 was a tank hit from behind and was very much in a worse state than the one we're looking at here.
"The turret and the gun look as though they are still in tact. The tank is designed to take a lot of damage, unlike the Russian tanks. Hopefully it is recoverable."
My life inside a Challenger 2 tank
By Hamish de Bretton-Gordon
I commanded main battle tanks for around 24 years and would have spent thousands of hours in them.
Life in a tank is a unique environment which takes a bit of getting used to. You live and operate with three other tank soldiers, living in the closest proximity where there are no secrets.
You intermittently get to know everyone's strengths and weaknesses.
We are told at tank school that you will get to know your tank crew better than you know your mother - and that is not far from the truth.
I still remember vividly my tank crew from 24 years ago.
They were all Glaswegians - a pretty terrifying to somebody straight out of public school but are now some of my closest friends.
Sometimes you may be locked down in a tank for 24 hours and when you eat, sleep and do everything else you would do in that time, you get very close and learn to get along.
I never found it claustrophobic but it takes a lot of getting used to, especially the fact the tank can go in three different direction simultaneously.
The hull might be moving forward, the turret looking sideways and my commanders aiming site may be looking behind the tank, but you do master it.
Bizarrely it is very quiet in the turret even when you fire the main gun – all the noise of the tank is devastating for those close to the tank but not those in it.
In a similar fashion, artillery fire dropping close to the tank might not be noticed by the crew and unlikely to damage the vehicle.
In the First Gulf War my vehicle was hit by machine gun fire but I did not notice it until after the battle and I noticed that my sleeping bag which was attached to the outside was shredded.
Tank crews are unique people and bring "shock action" to the battlefield in a manner which no other military capability can.
Used correctly they are a game changer, as the Ukrainian army is showing us.
Used badly like the Russians are doing, they are little better than mobile coffins.
Britain was the first Nato ally to give Ukraine western main battle tanks earlier this year.
Former Defence Secretary Ben Wallace donated a squadron of 14 Challenger 2 tanks - which forced America and Germany to follow suit.
The Challenger 2s were assigned to Ukraine's elite 82nd Air Assault Brigade which was thrown into battle last month.
The tanks had been part of a strategic reserve to smash through cracks in Russian lines.
Mr de Bretton-Gordon said the footage of the tank could suggest Ukraine's counter-offensive is gathering pace.
The Challenger 2 was damaged on the frontline near Robotyne in the south - supporting Ukraine's claim that troops are close to smashing through Russia's lines of defence.
"The fact that Challenger 2s are up at the front might suggest things are moving rapidly," he said.
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"One would have thought the Ukrainians would have used their old Russian tanks first... then when they are close to breaking through, they would use the much faster and better protected Leopards and Challengers.
"It would appear to be roughly in the area where Ukrainians might be making significant progress."