The threat of terrorists crossing by ferry from Northern Ireland to Scotland is real, the former UK terrorism reviewer has warned.
Officers at Scottish ports Loch Ryan and Cairnryan said passenger information from ferry companies was "incomplete and unreliable".
David Anderson QC, who wrote a report before he left office at the start of March, said passenger lists for ferries connecting Belfast and Larne to the Scottish west coast were incomplete and unreliable.
"On my visits, the common and strongly expressed refrain from ports officers was they could do their jobs more effectively if they had better advance information about passengers arriving (and departing) by sea," he said.
Mr Anderson said the special importance of the routes was accentuated by the invisible land Border between the Republic and Northern Ireland.
"This requires great trust to be placed on the common travel area arrangements, since a terrorist who has managed to gain entry to the Republic can normally travel to Northern Ireland without passing a border check," he said.