Ukrainian forces unleashed British made cruise missiles on Russia for the first time on Wednesday.
In a dramatic development, up to 12 Storm Shadow rockets were fired at targets in Kursk – the southern Russian province where Kyiv troops have seized territory.
The Mail understands the attacks, which followed Ukraine firing US-supplied ATACMS missiles on Tuesday, were personally approved by Sir Keir Starmer.
They came a day after Vladimir Putin signed off on changes to the Kremlin’s nuclear doctrine.
These conditions authorise a nuclear response to any conventional attack on Russian soil – if the attacking state is supported militarily by a nuclear power.
Under the new terms, such an incident would be considered a ‘joint attack’ and leave the attacking state and its backers liable to nuclear reprisals from Moscow.
The move also came as Defence Secretary John Healey announced that several major military projects were being cancelled.
Meanwhile, 50,000 Russian and North Korean troops were preparing to launch a counter-offensive to liberate Ukrainian-held areas.
Prime Minister Keir Starmer speaks during a press conference on the sidelines of the G20 summit in Rio de Janeiro, Brazil, on November 19
This is the moment missiles believed to be British Storm Shadow missiles struck inside Russia
Russian President Vladimir Putin attends a meeting with New People party’s leader Alexey Nechaev in Moscow on November 19
Images being shared on social media show what appear to be fragments of a British Storm Shadow missile in Marino, Kursk
On Wednesday afternoon, Russian military bloggers recovered missile fragments and posted unverified images on social media. The pieces were seemingly stamped with the words Storm Shadow.
Multiple explosions could be heard – preceded by high-pitched whistling apparently from incoming missiles – in videos recorded near the village of Maryino. The footage also showed smoke rising from buildings.
Unconfirmed reports suggested Ukraine had targeted an underground command and control facility 50 miles inside Russia.
The navigational data and satellite intelligence which facilitated the air strikes was understood to have been provided by the US.
The strikes, which have not been confirmed by the British Government, follow the use of UK Storm Shadows to eliminate Russian military infrastructure in Crimea.
The significant difference is that while the UK regards occupied Crimea as Ukrainian sovereign territory, Kursk is recognised by Britain as belonging to Russia.
It is understood that the last time British weapons were used on Russian sovereign territory was during clashes between an Allied force and the Bolsheviks in the Arctic Archangel region in 1918-19. Before that it was during the Crimean War in the 1850s.
Speaking in the Commons, Mr Healey declined to confirm the reports or divulge any operational details.
One image shows a written indentation on a chunk of metal reading: ‘Storm Shadow’
The £800,000 rockets use GPS technology to precisely blast targets, and can travel through the air at 600mph
He told MPs: ‘We have seen over recent weeks a significant change in the [Russian] action and the rhetoric on Ukraine. We as a nation and a Government are doubling down on our support for Ukraine and intend to do more.’
Former British Army commander and chemical weapons expert Colonel Hamish de Bretton-Gordon told the Mail he hoped the move did not come ‘too late’ considering the state of the conflict.
He said: ‘Whoever controls Kursk at Christmas will be on the front foot ahead of ceasefire negotiations which could start when US President-elect Donald Trump takes office.
‘It is such a shame this decision was not taken months ago. Let’s hope Sir Keir Starmer learns from this.’
In another dramatic move, outgoing US President Joe Biden permitted Ukraine to use US anti-personnel mines in a bid to thwart the advance of Russian troops across its eastern provinces.
With disregard for the lives of its troops, who are forced to charge Ukrainian positions, Russia has seized six times as much territory this year than in 2023.
Speaking on GB News, Conservative Party leader Kemi Badenoch said supporting Ukraine was ‘the right thing’ as it was fighting a war on this country’s behalf.
With tensions at an unprecedented high, the US closed its embassy in Kyiv on Wednesday morning. The Italian and Greek embassies were also closed.