Police in England have made a series of arrests over the killing of police constable Yvonne Fletcher outside the Libyan embassy in London 31 years ago.
A Libyan man is being held on suspicion of conspiracy to murder.
Two other people are being questioned over money laundering offences.
Commander Richard Walton says police are also launching a social media campaign to try and trace a group of Pro-Gadaffi campaigners who were there that day: “We’re launching the largest Facebook appeal we’ve ever done in the Met,
“And we are hoping that those men will come to us and speak to us, particularly those who have never spoken to us before.”