He was regularly paid for information by the secret service and had a handler called “Martin” as he helped investigate Russian organised crime, a barrister for his widow Marina claimed.
In a dramatic twist, Ben Emerson QC, also claimed he was working with Andrei Lugovoi, the former KGB bodyguard who is the prime suspect in his death.
It came as it emerged submissions from the British Government concluded there is prima facie evidence that the Russian state was involved in Mr Litvinenko’s death.
Mr Litvinenko, a Russian dissident and former KGB agent, was allegedly poisoned by radioactive polonium–210 while drinking tea during a meeting with former security colleagues at the Millennium Hotel in Grosvenor Square in November 2006.
He died three weeks later in University College Hospital.