A former colleague of WPC Yvonne Fletcher says investigators are closer than they have “ever been” to achieving justice.
Former PC John Murray, who witnessed the 1984 shooting outside the Libyan embassy in London, is in Libya in a bid to bring her killer to justice.
He said a member of Libya’s new government had assured him that Matouk Mohammed Matouk would stand trial, if he is caught.
Matouk is the only suspect believed to be alive, but he is currently on the run from the new regime.
In August Libya’s new reconstruction minister, Farage Sayeh, told Channel 4 News that Scotland Yard detectives would be welcomed into the country to investigate the murder.
Yvonne’s mother Queenie Fletcher has previously said the toppling of the Gaddafi regime offers the “best chance yet” of bringing her daughter’s killer to justice.
John Murray was standing just yards from WPC Fletcher when she was gunned down and travelled in the ambulance to hospital.
He told the wounded policewoman, who was conscious at the time, that he would ensure her assailants were brought to justice.
“Twenty-seven years is a very long time but my trip here to Libya has brought me closer than ever to a final conclusion,” he told the BBC.
“It’s strange, here in Tripoli, the support from the Libyan people, the support from the NTC (National Transitional Council), they all know about Yvonne Fletcher, they all know what happened.
“They all know the people who were responsible and I’m really overwhelmed by their support.”
“We believe he (Matouk) is still in Tripoli,” Mr Murray said.
“The NTC are actively looking for him as well but I’ve got no doubt that very, very soon he will be detained.”
And he said that Abdul Hafiz Ghoga, the NTC’s vice-chairman, had offered him “tremendous hope”, stating that if the man is detained, he will be prosecuted and could be extradited to Britain.
WPC Fletcher was shot while policing a protest outside the Libyan embassy.
As she lay in an ambulance before she died, Mr Murray “cradled her head”, promising his colleague he would find her attackers.
“When she was still conscious, I said to her ‘Don’t worry, Yvonne, I will find the people who did this, don’t worry, we will get them’,” he said.
Last month rebel officials in Tripoli said one suspect, Abdulqadir al-Baghdadi, an official in the embassy at the time, had been shot in the head.
Junior diplomat Abdulmagid Salah Ameri, who was suspected of firing the fatal shots, was never traced after he was deported along with other embassy officials following an 11-day stand-off, and is thought to have died.