A former IRA leader who turned informer and then became a best-selling author, Sean O'Callaghan, has died aged 63.
It is understood Mr O'Callaghan died while swimming in a pool in Jamaica, where he was visiting his daughter.
The County Kerry native detailed the inner workings of the IRA in his book, The Informer, in 1999, and lived under the constant threat of reprisal.
He was jailed in the 1990s after walking into a police station in England and admitting two IRA murders.
Mr O'Callaghan joined the IRA in the mid-1970s, but by the end of the decade, he had turned informer and started providing information to the Irish police.
Among his revelations was the claim he thwarted a plot to murder the Prince of Wales and Princess Diana in the 1980s.
Senior republicans said Mr O'Callaghan's claims were exaggerated, or untrue.