 Police arrived at the embassy almost immediately after the first reports of gunfire , and , within ten minutes , seven DPG officers were on the scene . The officers moved to surround the embassy , but retreated when a gunman appeared at a window and threatened to open fire . Deputy Assistant Commissioner John Dellow arrived nearly 30 minutes later and took command of the operation . Dellow established a temporary headquarters in his car before moving it to the Royal School of Needlework further down Princes Gate and then to 24 Princes Gate , a nursery school . From his various command posts , Dellow coordinated the police response , including the deployment of <unk> , the Metropolitan Police 's marksmen , and officers with specialist surveillance equipment . Police negotiators made contact with Oan via a field telephone passed through one of the embassy windows , and were assisted by a negotiator and a psychiatrist . At 15 : 15 Oan issued the DRFLA 's first demand , the release of 91 Arabs held in prisons in Khūzestān , and threatened to blow up the embassy and the hostages if this were not done by noon on 1 May . 
