Derry IRA informer Raymond Gilmour has been found dead in his flat in Kent.
The Belfast Telegraph is reporting today that his body was lying there for up to a week and it was so badly decomposed that he had to be identified from photographs.
An autopsy is currently being carried out to determine the cause of death.
Fellow agent, Martin McGartland believes the security services now have blood on their hands.
Raymond Gilmour, gave evidence against 31 men and women in one of Northern Ireland's best known republican supergrass trials.
After the case collapsed in 1984, he moved to England were he was given a new identity by MI5.
In the years following his move to England, Gilmour suffered from alcoholism and serious psychological problems.
His friend and fellow agent, Martin McGartland, said that he spent years begging MI5 for financial and psychological help.
Instead, they turned their back on him and now have blood on their hands over his death.
McGartland says that Gilmour never regretted becoming an informer, he was immensely proud of what he did and believed it was the right thing to do.
His funeral is due to take place next week.