British police investigating the 1988 Lockerbie bombing are to visit Libya for the first time.
Following talks in Tripoli with Libyan prime minister Ali Zeidan, David Cameron said officers from the Dumfries and Galloway force had been granted permission to travel to the country.
"I am delighted that the Dumfries and Galloway Police team will be able to visit your country to look into the issues around the Lockerbie bombing," he told a joint news conference.
The breakthrough follows months of behind-the-scenes negotiations with the authorities in Tripoli, and detectives are now expected to travel to the country next month.
Although police investigating the murder of WPc Yvonne Fletcher - who was killed by shots fired from the Libyan People's Bureau in London in 1984 - have visited three times since the revolution in 2011, similar access had not previously been given to the Lockerbie team.
The only person to have been convicted of the attack, Libyan agent Abdelbaset al-Megrahi, died last year of prostate cancer, having been released by the Scottish Government on compassionate grounds after serving eight years of a life sentence.
Dumfries and Galloway Police want to investigate whether anyone else was involved in the attack, while the families of some of the victims remain convinced that it was nothing to do with Megrahi and he was an innocent man.
A spokesman for the force said: "It's the first time since the fall of the previous Libyan regime that officers will have the opportunity to make further inquiries in the country."
Two hundred and seventy people died when Pan Am flight 103 exploded over Lockerbie on December 21 1988 - including all 259 people on board and 11 town residents - in what remains the UK's worst terrorist atrocity.
Following the overthrow of Colonel Muammar Gaddafi, a formal request was sent to the Libyan government in February last year requesting access to the country for police and prosecutors investigating the bombing. The request was followed by a meeting in London between Scotland's top law officer the Lord Advocate, Frank Mulholland QC, and the Chief Constable of Dumfries and Galloway Constabulary, Pat Shearer, and the UK families of the victims.