What an odd answer. I'm afraid I don't define myself as a person governed by May: I'm a Brit in Britain and don't need such weird constructions! Theresa May is Prime Minister at the moment, but that's temporary.
However, there have certainly been mysterious deaths and known murders in the UK, if that's your underlying question. (I'm assuming you didn't mean to exclude murders by Russians in the UK, although that's how your words come across.)
There has, sadly, been a murder even after the Skripals were attacked: Nikolai Glushkov, an opponent of Putin. Recent and as yet unsolved.
Who was Russian businessman Nikolai Glushkov?
www.bbc.co.uk/news/world-europe-43435003
Glushkov was a friend of Boris Berizovsky, the man who gave Putin his break but who also later opposed him. Coroner gave an open verdict on Berizovsky's death.
www.independent.co.uk/news/world/europe/the-weird-world-of-boris-berezovsky-alexander-litvinenkos-inquest-has-provided-an-intriguing-insight-10117927.html
Dr Matthew Puncher was found dead after working in Russia.
The Man Who Knew Too Much
His nuclear research helped a judge determine that former Russian spy Alexander Litvinenko had been assassinated – likely on Putin’s orders. Just months after the verdict, the scientist himself was found stabbed to death with two knives. Police deemed it a suicide, but US intelligence officials suspect it was murder.
www.buzzfeed.com/janebradley/scientist-who-helped-connect-litvinenkos-murder-to-the?utm_term=.knQMZqqvv#.xy1rk99qq
Actually that article, and the others in the series, may be worth reading.
And then of course there are deaths and mysteries that have no known links to Russia, like the disappearance of Richey Edwards.
But what the Russian-linked deaths have in common – in the UK, in Russia, and elsewhere in the world – is an unusually large number of attacks and deaths among opposition politicians, diplomats, investigative journalists, and people who are about to testify about Russia-related corruption. Probably some of those are natural deaths (Russian whistleblower Alexander Perepilichnyy's might have been), and Russian mobsters are out of control so some deaths could simply be them exporting their feuds.
But some... Well, there's a reason for choosing polonium. It's not meant to leave doubt.