 The two SAS teams on @-@ scene — Red Team and Blue Team — were ordered to begin their simultaneous assaults , under the codename Operation Nimrod , at 19 : 23 . One group of four men from Red Team abseiled from the roof down the rear of the building , while another four @-@ man team lowered a stun grenade through the skylight . The detonation of the stun grenade was supposed to coincide with the abseiling teams detonating explosives to gain entry to the building through the second @-@ floor windows . Their descent had not gone according to plan and the staff sergeant leading the <unk> became entangled in his rope . While trying to assist him , one of the other soldiers had accidentally smashed a window with his foot . The noise of the breaking window alerted Oan , who was on the first floor communicating with the police negotiators , and he went to investigate . The soldiers were unable to use explosives for fear of injuring their stranded staff sergeant , but managed to smash their way into the embassy . 
