An ex-KGB agent is to be charged in connection with the murder of poisoned former Russian spy Alexander Litvinenko, the Crown Prosecution Service said.
A warrant has been issued for the arrest of Moscow-based Andrei Lugovoy, although there is no extradition treaty with Russia.
Director of Public Prosecutions Sir Ken Macdonald said the case was "clearly in the public interest".
Sir Ken described the murder as an "extraordinarily grave crime".
He said: "I have today concluded that the evidence sent to us by the police is sufficient to charge Andrei Lugovoy with the murder of Mr Litvinenko by deliberate poisoning.
"I have further concluded that a prosecution of this case would clearly be in the public interest.
"I have instructed CPS lawyers to take immediate steps to seek the early extradition of Andrei Lugovoy from Russia to the United Kingdom, so that he may be charged with murder - and be brought swiftly before a court in London to be prosecuted for this extraordinarily grave crime."
The full CPS charge is that Lugovoy murdered Mr Litvinenko on November 23, 2006.
Mr Litvinenko died in hospital in London after being poisoned with the radioactive agent Polonium-210. The former KGB officer was a fierce critic of President Vladimir Putin's Kremlin regime and had been granted political asylum in the UK.
Sir Ken said Mr Litvinenko died of "acute radiation injury" after ingesting a lethal dose of Polonium.