Hundreds of convicted terrorists from the Ulster Troubles are “virtually invisible” to police in the rest of Britain because of a computer glitch.

The Police National Computer is not linked to the criminal database in Northern Ireland, meaning that the criminal records of many serious figures from the province’s past, now living in England, Scotland and Wales, are not available to police officers Counter-terrorism sources say that in light of the upsurge in terrorist activity in Northern Ireland, including the Real IRA murders of two soldiers and the discovery of a series of unexploded bombs, there are mounting security concerns about the situation.

A report by Sir Ian Magee, a former civil servant, said that correcting the problem was an urgent issue that would cost millions to resolve.

The Times has learned that police in northwest England recently stopped a man of whom they were suspicious but computer checks revealed no relevant information. The officers’ unease led them to carry out an internet search on the man’s name when they returned to their station. It was only then that they discovered they had stopped Johnny Adair, former commander of the notorious “C” company of the Ulster Freedom Fighters.

Adair, 46, nicknamed “Mad Dog”, has a conviction for directing terrorism in the 1990s and was exiled from Northern Ireland by his former loyalist colleagues after a violent feud. But none of that information was available to the officers who stopped him, because of the incompatibilities in police computer systems.

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