A British former detective who investigated the murder of Alexander Litvinenko has told ITV News he believes he was also poisoned in an apparent attack ordered by the Kremlin.
Video report by Security Editor Rohit Kachroo
Brian Tarpey, a former detective inspector, believes Russian government officials spiked his tea to unsettle him and colleagues looking into the case.
Litvinenko, a former Russian spy and fierce critic of Putin's regime, was infamously killed in London in 2006 after his cup of tea was poisoned with radioactive polonium-210.
Tarpey, who led the murder investigation, has told ITV News of how he believes he was poisoned on a trip to Moscow to question the main suspect in the killing.
Tarpey and a colleague paid a visit to the prosecutor general’s office.
The Russians had allowed him to interview suspect Andrey Lugovoy - on the condition that they made the recordings.
These tapes were later withheld from Scotland Yard.
Tarpey is featuring in the upcoming Channel 4 documentary Hunting the KGB Killers.
A judge-led inquiry found President Vladimir Putin "probably" approved the assassination of Litvinenko.