The widow of murdered former KGB spy Alexander Litvinenko has won a High Court victory raising her hopes of obtaining a public inquiry into her husband's death.
Marina Litvinenko challenged the UK Government's decision to await the outcome of a normal inquest before deciding whether there should be an inquiry with powers to probe more deeply into the killing.
Now three High Court judges have decided that Home Secretary Theresa May must reconsider the decision in the light of their ruling.
Mrs Litvinenko's lawyers described it as "a very strong ruling".
The judges gave the Government until Friday to decide whether to lodge an appeal.
Speaking for the three judges, Lord Justice Richards said: "Taking everything together, I am satisfied that the reasons given by the Secretary of State do not provide a rational basis for the decision not to set up a statutory inquiry at this time but to adopt a 'wait and see' approach."
Quashing the decision, the judge said: "The deficiencies in the reasons are so substantial that the decision cannot stand."