A number of reports since the weekend have quoted sources in the Metropolitan Police as saying that the activities of its anti-terrorist units are being stepped up.
It was also claimed that this followed reports that dissident republicans associated with the "Real" IRA may already have a bombing team in place in Britain.
However, senior Garda sources said they were confident "Real" IRA plans to carry out bombing attacks in Britain or Northern Ireland had been undermined by Special Branch action in the past two months.
The Special Branch uncovered bomb-making equipment including materiel bought in former Yugoslavia by the dissidents.
It is believed a quantity of TNT explosives and detonators might have been intended for bomb attacks on police stations or loyalist targets in the North.
According to the sources, one leading dissident republican from the Louth-Monaghan Border area has been abroad since late spring, and it is believed he had been attempting to buy weapons in Spain and former Yugoslavia.
He was previously involved with the group known as the Continuity IRA and was involved in the manufacture of a number of large bombs which were intercepted by gardai in the Inniskeen area in 1994.
His present whereabouts are not known, and it is possibly that his disappearance might have prompted the review of security arrangements in Britain.
There are concerns among security forces on both sides of the Border that dissidents will try to disrupt the political process in the North with some act of terrorism.