NATO Article 5 is all you need to know.
That means that if Russia were to step even one Russian Soldier’s foot on sovereign UK territory or make one strike, then the entire military, economic and industrial might of all NATO nations mobilize against Russia. Russia nuking London is one big ‘IF’ in the first place.
The UK currently has around 150,000 Russians living there. 73,000 of these live in London. Putin would literally be massacring more Russians in his first strike than they’re going to lose in another year of fighting at this rate.
On top of that, there are thousands and thousands of people from every other nation living there. There would be a global panic to find and locate the dead from every country in the world who has just lost thousands of its citizens and Russia is going to burden that.
Russia is all too aware that Britain has around 240 nuclear weapons of its own, which can be fired from submarines from anywhere on the globe to anywhere on the globe. The French has about 290 and the USA boasts about 4,000 – that actually out-nukes the Russians stock of about 4200.
And if Putin eventually make its threat happen; in exchange for the thermonuclear destruction of London, Britain might opt to take out Russian nuclear facilities so that Russia can’t build any more nuclear weapons, take out their remaining nuclear weapons also and take out the rail yards and power stations of all cities surrounding Moscow.
