He described it as a "deeply distressing development" and a judgement he would "go over in my mind 100 times".
The prime minister looked and sounded profoundly affected by the news that he had to unveil at his Downing Street news conference - that British aid worker Linda Norgrove may have died as a result of a hand grenade detonated by her would-be American rescuers.
Update 1314: The prime minister's news conference was delayed by almost an hour this morning as he was determined to speak to the Norgrove family before answering questions in public about the death of their daughter Linda. The family lives on the isle of Lewis and has no phone. The mobile signal on the island is unreliable. A liaison officer was sent to the island this morning to help arrange the call.