7 McCANN AND OTHERS v. THE UNITED KINGDOM JUDGMENT E continuing to brief the soldiers under his command but in the same location. The Commissioner also explained the rules of engagement and firearms procedures and expressed the importance to the police of gathering evidence for a subsequent trial of the terrorists. 23. The briefing by the representative of the Security Services included inter alia the following assessments: (a) the IRA intended to attack the changing of the guard ceremony in the assembly area outside Ince’s Hall on the morning of Tuesday 8 March 1988; (b) an ASU of three would be sent to carry out the attack, consisting of Daniel McCann, Sean Savage and a third member, later positively identified as Mairead Farrell. McCann had been previously convicted and sentenced to two years’ imprisonment for possession of explosives. Farrell had previously been convicted and sentenced to fourteen years’ imprisonment for causing explosions. She was known during her time in prison to have been the acknowledged leader of the IRA wing of prisoners. Savage was described as an expert bomb-maker. Photographs were shown of the three suspects; (c) the three individuals were believed to be dangerous terrorists who would almost certainly be armed and who, if confronted by security forces, would be likely to use their weapons; (d) the attack would be by way of a car bomb. It was believed that the bomb would be brought across the border in a vehicle and that it would remain hidden inside the vehicle; (e) the possibility that a "blocking" car - i.e. a car not containing a bomb but parked in the assembly area in order to reserve a space for the car containing the bomb would be used had been considered, but was thought unlikely. This possibility was discounted, according to Senior Security Services Officer O in his evidence to the inquest, since (1) it would involve two trips; (2) it would be unnecessary since parking spaces would be available on the night before or on a Tuesday morning; (3) there was the possibility that the blocking car would itself get blocked by careless parking. The assessment was that the ASU would drive in at the last moment on Monday night or on Tuesday morning. On the other hand Chief Inspector Lopez, who was not present at the briefing, stated that he would not have brought in a bomb on Tuesday since it would be busy and difficult to find a parking place. 1. Mode of detonation of bomb 24. Various methods of detonation of the bomb were mentioned at the briefing: by timing device, by RCIED (radio-controlled improvised explosive device) and by command wire. This last option which required placing a bomb connected to a detonator by a wire was discounted as impracticable in the circumstances. The use of a timer was, according to O, considered highly unlikely in light of the recent IRA explosion of a bomb