Libya's interim Prime Minister Abdurrahim El-Keib has laid a wreath at the spot where policewoman Yvonne Fletcher was shot dead outside the country's London embassy in 1984.
Mr El-Keib visited the scene after it was announced a team of detectives from the Metropolitan Police would fly to Libya to continue their investigations into the unsolved murder.
The Libyan premier bowed in front of the memorial to WPC Fletcher and laid a wreath of white roses and carnations at the spot.
No-one has ever been brought to justice for the killing, but Mr El-Keib said his country would "work very closely together" with the UK after talks with Prime Minister David Cameron.
WPC Fletcher was shot dead as she policed an anti-Gaddafi demonstration outside the Libyan People's Bureau in London - by a bullet apparently fired from within the building.
The investigation has always been open and the Met Police have described the visit to Libya as "significant".
Commander Richard Walton, head of the Counter Terrorism Command, said: "We have never lost our resolve to solve this murder and achieve justice for Yvonne's family."
Mr Cameron met Mr El-Keib, Scotland Yard officers and Home Office minister James Brokenshire to discuss the case.
Mr El-Keib worked with those opposed to the Gaddafi regime during the late leader's dictatorship and said he knew some of those involved in the demonstration in London, which led to an 11-day siege of the building in St James's Square and the severing of diplomatic links between the UK and Libya.
Fresh hopes were raised in the search for WPC Fletcher's killer when Colonel Gaddafi was ousted last year, but plans to send British police to Libya have been hampered by the lack of co-operation from the authorities in Tripoli.
During his meeting with Mr Cameron, Mr El-Keib paid tribute to the UK's role in the international military mission to protect civilians from Col Gaddafi's forces.
He told the PM: "You took a bold decision when it was very difficult for many to even consider supporting the Libyan people. You took that decision which inspired many of us."
Mr Cameron told him: "There are huge challenges for your country - challenges we want to help you with.
"We really believe in the Arab Spring and what you achieved in Libya. We will be backing you every step of the way."
Elections for a national assembly for Libya are expected in June or July.
With the meeting coming days after the death of the only person convicted of the Lockerbie bombing, Abdelbaset al Megrahi , the two leaders were also expected to discuss whether any other evidence relating to the atrocity has emerged since Col Gaddafi's downfall.