Petraeus tells Cameron: Linda Norgrove death inquiry is 'personal priority'

US General David Petraeus tonight pledged that finding out how British aid worker Linda Norgrove died was his "personal priority". The commander of the Nato-led campaign in Afghanistan discussed the case with David Cameron when the men held talks in Downing Street this afternoon. It emerged earlier this week that Norgrove may have been killed by a grenade detonated by US special forces as they tried to free her from Taliban holding her captive. Speaking after the meeting this evening, a Number 10 spokesman said Cameron had raised Norgrove's case. "General Petraeus said that the investigation was a personal priority for him and emphasised that there would be full cooperation between the US and UK," the spokesman said. Petraeus's visit to No 10 follows reports that Norgrove was killed after a US special forces soldier failed to see that she had broken away from her captors. The Guardian has learned that Norgrove was already lying in a foetal position to keep safe when an American grenade was thrown during an attempt to rescue her on Friday night. A US-UK investigation is under way to establish what happened. US officials initially said Norgrove, 36, died after one of her captors detonated a bomb vest but it later emerged that she may have been killed by a grenade thrown by US troops. Petraeus had already been due to meet Cameron before the incident, but will now have the opportunity to discuss it in person. The Guardian has learned that a US special forces soldier who is believed to have accidentally killed Norgrove is likely to face disciplinary action after failing to inform his commanding officers that he had used a grenade until long after the event. Sources in Kabul and London have confirmed that during the assault on the kidnappers' hideaway the hostage broke away from her captors and lay in a foetal position to avoid harm. The soldier from the elite Seal Team Six special forces unit failed to see Norgrove and tossed his fragmentation grenade in, which exploded next to her. It has also emerged that: • US forces monitored the kidnappers using a network of informers and drones. • Conversations were intercepted indicating Norgrove could be executed "like the Russian" or shipped across the Pakistan border. • British officers working with the Americans were kept informed of the intelligence at all times. • The entire mission was relayed on to six widescreen televisions back at the command centre, yet Norgrove's death was first attributed to an insurgent detonating a suicide vest – an account that was reported around the world. The use of the grenade was first discovered when the taskforce commander reassessed surveillance video of the attack and saw the Seal toss the grenade into the compound four seconds before the blast. Absolute certainty about the cause of death will have to await the official results of an autopsy but senior officers are almost sure that the investigation will show the US grenade was responsible. The prime minister, who has already spoken with the general and with Barack Obama about the incident by telephone, said yesterday that the picture was still "unclear" about how the hostage situation had ended. He added: "It is an impossibly difficult decision to make about whether to launch a raid and try to free a hostage. "In the end we must all be clear: the responsibility for Linda's death lies with those cowardly, ruthless people who took her hostage in the first place." Petraeus and other top commanders are said to be greatly distressed that a misleading account of the raid was initially provided to the British government, and concerned about the potential damage to the bilateral relationship. "Petraeus was very clear that he wanted to flag something was wrong with the original account," a Downing Street source said. "They took another look at the video and immediately called us." Originally from Sutherland in the Scottish Highlands, Norgrove was working for the US firm Development Alternatives Inc (DAI) in the east of Afghanistan when she was seized by militants in Kunar province on 26 September. Petraeus, supreme commander of Nato troops in Afghanistan, will also be learning from the prime minister about the keenly anticipated defence review to be announced next week. He will want reassurance about the impact of cuts at the Ministry of Defence on the UK's role in Afghanistan. There have been concerns in Washington that any scaling back of British defence capabilities may have implications for the UK's ability to support the US in future deployments.