Scottish authorities said on Thursday they wanted to interview defecting Libyan foreign minister Moussa Koussa over the 1988 Lockerbie bombing, pleasing victims' relatives.
Koussa, also the former spy chief for Muammar Gaddafi, fled to Britain on Wednesday, parting ways with the Libyan leader over what a friend of Koussa called Gaddafi's attacks on civilians in his conflict with rebels.
Families representing some of the 270 people killed when Pan Am Flight 103 exploded over the Scottish town of Lockerbie said no deals should be done to protect Koussa.
"This could be all the evidence that we wanted given to us on a silver platter," Frank Duggan, president of the Victims of Pan Am 103 group in the United States, told Reuters.
Libya's Foreign Minister Moussa Koussa holds a news conference in Tripoli in this March 18, 2011 file photo
While British officials are hoping that he will provide vital military and diplomatic intelligence, campaigners want him to shed light on the bombing which killed 259 people, mostly Americans, on the plane and 11 on the ground.
"He was the head of the Libyan intelligence services so if Libya is responsible for the bombing of Pan Am 103 then Mr Koussa is too," Pamela Dix, whose brother was one of those killed, told Reuters. "He should not be a free man in this country."
Noman Benotman, a senior analyst at Britain's Quilliam think tank, said his friend Koussa was "very positive to cooperate not just with the UK government, but Europe as well."
When asked by Channel 4 News if Koussa was ready to face justice, Benotman replied: "Of course, without a doubt, trust me on that.
"But the point is there is no official case against him -- there's a lot of rumors and a lot of loose talk in the media here and there, but as far as I am concerned there is no legal issue, he is not being attached to any terrorist act."
Abdel Basset al-Megrahi, a former Libyan agent, was sentenced to life in prison in 2001 for his part in blowing up the airliner but was released by the Scottish government in 2009 when he was judged by doctors to be terminally ill with prostate cancer.
Koussa played a key role in the release of Megrahi, who is still alive.
British Foreign Secretary William Hague said Koussa would not be given immunity from prosecution. Prime Minister David Cameron said police and prosecutors would be free to pursue any evidence.
Cameron has repeatedly condemned Megrahi's release and criticized the policy of Britain's former Labour government to restore diplomatic ties and business links in return for Gaddafi ending his attempts to obtain banned weapons.
"(Former Prime Minister) Tony Blair ... chose British business interests effectively over uncovering the truth around Lockerbie," Dix said. "So David Cameron is going to have to deliver. I will be expecting a great deal and I will not be expecting deals to be done."