Two Putin attacks in the UK in recent years need to be taken into account. In 2006, Alexander Litvinenko, a defecting KGB and FSB officer, was poisoned in London with Polonium added to his tea. He was so radioactive that he was buried in a lead coffin.
https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvinenko
And then in March 2018, two identified Russians travelled to Salisbury with USSR era Novichok nerve agent (one of the most potent ever made) in a perfume bottle, and sprayed the door handle of a Russian double agent's house with the stuff. He and his daughter were hospitalized for weeks but ultimately survived. They then astonishingly dumped the perfume bottle in a waste bin, where it was found and then used with fatal consequences.
There was a major cleanup with teams in full hazmat gear that went on for days.
https://en.wikipedia.org/wiki/Poisoning_of_Sergei_and_Yulia_Skripal
Both of these attacks on UK soil were widely reported, their perpetrators identities known and absolutely identified as being initiated with Putin's knowledge.
And what did we do? Precisely fucking nothing.