If you thought relations between the United Kingdom and Russia had hit rock bottom after the attempted murder of former Kremlin spy Sergei Skripal on British soil, you may have to think again.

On Friday afternoon, London police announced that the death of another Russian exile, Nikolay Glushkov—a vocal Putin critic who was wanted in Russia and previously predicted he would be assassinated—is being treated as murder.

While the London-based Metropolitan Police have made clear that “at this stage” there is no connection to the attempted murders of former spy Skripal and his daughter, the revelation that Glushkov was apparently killed—this time by "compression of the neck"—will do nothing to calm the diplomatic crisis between Russia and the West, particularly because of his close links to other controversial Russian exiles.

Glushkov was a close friend of exiled Russian tycoon Boris Berezovsky, suspected by Glushkov to have been murdered on Kremlin orders in 2013.

Friday's police statement made clear that counter-terrorism police are leading the investigation into the murder, rather than local police, "because of the associations Mr Glushkov is believed to have had."

Those associations include a group of Russian exiles who have died in mysterious circumstances in Britain over the past few years. Glushkov spoke to The Guardian in 2014 about the “hit-list” of Russian exiles such as Berezovsky, his business partner Badri Patarkatsishvili who died in 2008, and former Russian intelilgence officer Alexander Litvinenko, who was killed with radioactive poison in London.

Glushkov voiced his belief that the Kremlin was methodically killing fellow exiles on a hit-list and said gloomily: "I don't see anyone left on it apart from me."

Berezovsky's death is one of 14 being reinvestigated by British police and intelligence in the wake of the attempted Skripal murders, though no foul play was found in any of the deaths at the time.

Glushkov was granted political asylum in the U.K. in 2010. In 2016, the British government refused a request from Russia to hand him over on fraud charges connected to a period in the 1990s when he was a high-ranking executive in the Russian national airline Aeroflot. In a trial in absentia in Russia in 2017, he was sentenced to eight years in prison.

On Monday, Glushkov was reportedly due to defend himself against the fraud claims made against him in a commercial court in London. He never showed up and was, later that day, found dead.

Along with his friend and former colleague Berezovsky, he fell out with Putin as their fortunes waned under his presidency. Russian exiles in the U.K. are believed to have established close ties—Berezovsky was known to be friends with Litvinenko, and Glushkov told the inquiry into Litvinenko's death that he'd met the former spy in Berezovsky's office.

Glushkov was also known for having given evidence against the owner of Chelsea Football Club, Russian oil oligarch Roman Abramovic, who remains on good terms with Putin and the Kremlin, in a 2011 court case.

Police appealed for information from the British public.