The senior Scotland Yard official who led the investigation into the poisoning of Alexander Litvinenko welcomed the Russians’ offer of talks yesterday and said that police should explore it fully.

Andy Hayman, the former Assistant Commissioner of the Metropolitan Police, said: “There has been a victim of a murder and a surviving family who seek justice. While people who are alleged to be connected with that are making what appear to be interesting offers of cooperation, those offers must be put against the distressing background for the family.

“That said, it’s important that no opportunity should be dismissed out of hand. I am sure the authorities would look to develop this offer further.”

Lawyers say that British prosecutors have powers to grant immunity from arrest to suspects wanted by London but cannot extend that protection to those sought by European neighbours.

James Lewis, QC, an extradition specialist, said: “The Director of Public Prosecutions could in theory give Mr Lugovoy immunity because that’s a matter of English law and there are no international obligations.” However, the European Arrest Warrant system has no such room for “executive discretion”. If Germany, whose detectives have been investigating Mr Kovtun’s polonium trail, sought extradition, Britain would have to comply.

Alex Goldfarb, a friend of Litvinenko and co-author with his widow, Marina, of Death of a Dissident, said: “These two people are playing games because they know that their bluff will not be called. They want to create a positive PR effect and make it appear as if they are ready to cooperate with the investigation.” dkennedy@thetimes.co.uk

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