Key witnesses in the Alexander Litvinenko investigation are missing, with their families claiming that they fear for their lives.
The sudden disappearance of a number of leading figures linked to the affair will make it even harder for British detectives, whose inquiry has now spread across five countries.
Interpol joined the hunt for the murderer yesterday, saying that it hoped to exchange information coming from Britain, France, Italy, Germany and Russia.
Scotland Yard was struggling to gain access to vital witnesses with former associates of Litvinenko claiming that they are too scared to come forward.
Evgeny Limarev, who told the former KGB officer that he was on a death list just hours before he was poisoned, was reported to have fled his home in the French Alps, where he was under police protection. Before his disappearance, he said that British detectives wanted to question him about the origins of a hitlist that included Litvinenko’s name among the targets being hunted by a team of former Russian agents working across Europe.