A retired British army brigadier has told the Smithwick Tribunal that it would have been impossible for the IRA to mount the ambush in which two senior RUC officers died in under three hours.

However, as the RUC men Chief Supt Harry Breen and Supt Bob Buchanan, only left Newry RUC Station two hours before their death, this would mean that the mobilisation of men and weapons had already begun an hour before they left.

Brigadier Ian Lisles spent 14 years in Northern Ireland, much of that time in South Armagh.

He told the tribunal today that the IRA in that area were "extremely professional and extremely risk adverse."

If there was a chance an operation would not be a success from their point of view, they would cancel it.

Their attitude would also be that they could always come back another day. Time was always on their side, he said.

The brigadier said it was his experience that the IRA in South Armagh never did anything ad hoc. All their operations were "well planned and generally well executed."

To mount an operation the size of the one in which the two RUC men were killed would have taken considerable organisation as several roads would have to have been covered. It was impossible for them to have done it in under three hours at an absolute minimum, he said. Ideally, they would have needed between five and eight hours.

It was put to him that the earliest the RUC officers could have been seen heading for Dundalk was around 1.40pm, arriving in Dundalk at around 2pm. Brigadier Lisles said he did not believe that was enough time. The ambush took place at around 3.40p.m.

He also told the tribunal that he had seen intelligence reports relating to the killings and there was "absolutely no information" that there was a telephone tip off to the IRA about the visit of the RUC men.

The tribunal is investigating claims that a garda in Dundalk alerted the IRA to the meeting, allowing them time to set up the ambush.

Another retired senior British officer was asked if he was aware of RUC and British military intelligence which showed that there had been an increase in radio traffic among subversives in south Armagh at around noon on the day of the murders.

Brigadier Mike Smith said, however, that he could not comment as he did not know. He was not serving in Northern Ireland at the time of the attacks.

Brigadier Smith served seven tours of duty in Northern Ireland, the last one ending in 1997. He said that the IRA in South Armagh "were among the most capable and experienced terror groups."

He told the tribunal that he did not believe the operation was an attempt to kidnap the two officers. It was just an operation to kill them. The brigadier also said that the number of rounds fired during the attack at just 28 showed there was “controlled fire” by those involved. The pattern of fire, he added, did not suggest any element of panic among those involved.

Asked about how long it would take to organise the ambush, Brigadier Smith said that as an officer, he would not have liked to try and arrange a major operation within two hours.