Police believe that dissident republications planted a bomb on a lorry bound for an Irish Sea ferry to detonate it on Brexit day.
Officers have blamed the Continuity IRA for the botched terror bid planned for January 31st, after Belfast newspaper the Irish News received a coded warning that evening that a device had been left on a trailer in Belfast docks.
George Clarke, Police Service of Northern Ireland Assistant Chief Constable in charge of Brexit, said the warning was “sparse and limited”.
He said it claimed that the bomb would be on the midnight ferry, when there was no ferry scheduled to depart at that time.
A major police search operation instead focused on a late night Stenaline ferry to Cairnryan. When nothing was found, the ferry was allowed to sail at 11.16pm.
The newspaper then received a further call on Monday.
“That call contained substantially more detail,” said Clarke.
“It gave us the detail of a commercial haulage company and it indicated that the device had been left on a vehicle on a trailer connected to that company and the intention had been for that device to explode on Friday evening at around the time the United Kingdom left the European Union.”
The device was finally discovered at the premises on Monday night after an intensive police search operation.
The renegade group is alleged to have entered the yard of a company specialising in the transportation of frozen goods and attached the bomb to a heavy goods vehicle they appear to think was destined for a late night ferry crossing to Scotland.
Officers believe the dissidents selected the wrong vehicle, as the trailer containing the bomb did not leave its premises on the right day.
Clarke accused CIRA of “callous and reckless” behaviour that could have exposed the public to huge risk.