 As the deadline of noon approached , set the previous day for the release of the Arab prisoners , the police became convinced that the gunmen did not have the capability to carry out their threat of blowing up the embassy , and persuaded Oan to agree to a new deadline of 14 : 00 . The police allowed the deadline to pass , to no immediate response from the gunmen . During the afternoon , Oan altered his demands , requesting that the British media broadcast a statement of the group 's grievances and for ambassadors of three Arab countries to negotiate the group 's safe passage out of the UK once the statement had been broadcast . At approximately 20 : 00 , Oan became agitated by noises coming from the Ethiopian Embassy next door . The noise came from technicians who were drilling holes in the wall to implant listening devices , but PC Trevor Lock , when asked to identify the sound , attributed it to mice . COBRA decided to create ambient noise to cover the sound created by the technicians and instructed British Gas to commence drilling in an adjacent road , supposedly to repair a gas main . The drilling was aborted after it agitated the gunmen , and instead British Airports Authority , owner of London Heathrow Airport , was told to instruct approaching aircraft to fly over the embassy at low altitude . 
