A former security adviser to Sinn Fein leader Gerry Adams wept as he recalled being warned he and his family could be murdered by IRA assassins.
The recruitment company boss - who cannot be identified for legal reasons - said a caller, using the Provisionals nom de guerre "P O'Neill", left him "completely numbed and shocked" when he was told he and his business partner had been "investigated".
He said he was instructed to wait for a letter and "follow instructions".
Four days later - by which time he had contacted police - it arrived. A similar one was delivered to his colleague.
Both bore the Irish Gaelic for the Provisional IRA - Oglaigh na h-Eireann - and ended with the terror group's "historical signature".
It claimed a "prolonged and intensive investigation" had established the men had used the organisation's name for "personal gain" and pocketed £6m.
The former Sinn Fein supporter was told he, in particular, had abused the "position of trust" he once held.
It warned such behaviour was forbidden under the IRA's constitution, that the punishment for it was "self-explanatory", and that they ought to be "aware of the consequences".
Finally, it demanded payment of £150,000 within a week, warning if they contacted police "Fort Knox will not be safe for either you or your extended family".
Asked by prosecutor Mark Heywood what the consequences mentioned might be, the businessman wept as he replied: "Sir, that these people were going to shoot and kill me, my family and children."
He was also questioned about his understanding of the phrase "appropriate action" being taken if the matter was reported to police.
"I was under no mistake, sir, that this meant my entire family, including my children, my vulnerable, innocent, defenceless children, my elderly parents, the whole of my extended family, were threatened, their lives were threatened by this."
In the dock are former IRA prisoners Nick Mullen, 61, of Burlington Mews, West Acton, west London, and Ronald McCartney, 56, of Ross Road, Belfast.
The court has heard Mullen was jailed for 30 years in June 1990 after being found guilty of conspiracy to cause explosions.
McCartney, the longest-serving IRA prisoner, was released as part of the Good Friday Agreement after serving 21 years for trying to kill three policemen in Southampton in the 1970s.
Both men deny two counts of conspiracy to blackmail.
© Press Association