A prime suspect in the killing of Alexander Litvinenko will be allowed to give evidence to the inquiry into the former Russian spy's death.
Dmitri Kovtun will provide testimony by video-link after he was granted "core participant status" by the hearing's chairman Sir Robert Owen.
Kovtun and Andrei Lugovoi are suspected of murdering the 43-year-old, who died nearly three weeks after consuming tea laced with polonium-210 in London in November 2006.
The pair deny any involvement and remain in Russia, having initially refused to take part in the inquiry, which is sitting at the Royal Courts of Justice in London.
However, in March Kovtun dramatically changed his mind and offered to give evidence.
Sir Robert said earlier this year that he would grant him core participation status and allow him to give evidence if he meets a number of conditions.
A statement issued by the inquiry tonight confirmed: "Sir Robert Owen, Chairman of the Litvinenko Inquiry, has designated Mr Dmitri Kovtun as a Core Participant to the Inquiry, pursuant to rules 5(2)(a) and (c) of the Inquiry Rules 2006.
"Sir Robert is satisfied that Mr Kovtun has complied in full with his directions dated 2 April 2015.
"In complying with the directions Mr Kovtun has said that he is willing to: 1) attend a video-link evidence session in Moscow on dates specified by the Chairman; 2) cooperate with the inquiry regarding arrangements for that evidence; and 3) that he does intend to assert the privilege against self-incrimination."
No precise date has been given yet for the evidence but it is expected to be heard in late July.
On his deathbed, Mr Litvinenko accused Russian president Vladimir Putin of ordering his assassination - which the Kremlin denies.
In April Kovtun said he believes the former KGB officer might have killed himself accidentally after handling radioactive material.
He reportedly told a press conference in Moscow: "I am more than sure that he dealt with polonium, without knowing it.
"Maybe it was leaking and polonium accumulated in his body gradually. It is possible that something he carried with him led to a gradual accumulation of polonium in the body."
In April Kovtun was told to supply a number of details to the inquiry.
These included disclosing whether he will assert or waive his privilege against self incrimination when giving evidence.
His declaration that he would assert the privilege means that he may decline to answer any question that he believes could incriminate him.