A Libyan man has been arrested at his home in South East England on suspicion of conspiracy to murder PC Yvonne Fletcher, who was fatally shot outside the Libyan embassy in London three decades ago.
The man, in his fifties, who has not been named, was arrested at around 9am on Thursday morning.
He and two other Libyans – a woman in her forties from the same area and a man in his thirties from London – were also arrested, on suspicion of money laundering.
Fletcher was shot dead on 17 April 1984 while policing a protest outside the Libyan People's Bureau in St. James's Park by supporters of then Libyan leader Muammar al-Qaddafi alongside a counter-demonstration by anti-Qaddafi protesters.
Police say a number of shots were fired from within the bureau, including some from automatic weapons, and Fletcher was hit in the back. She died a short time later in Westminster hospital.
No one has ever been prosecuted over her death.
Commander Richard Walton, the head of the Met's counter-terrorism command, said on Thursday that the arrests this morning were "significant to the investigation".
"The day Yvonne was shot remains one of the saddest and darkest days in the history of British policing," he said.
"We have never lost our resolve to solve this case and to bring to justice those who conspired to commit this act of murder."
Walton said the arrests had resulted from lines of inquiry that had opened up since the regime change in Libya following the removal of Qaddafi in 2011.
Since then, the Met has dispatched teams of officers to Libya on at least seven different occasions to continue the inquiry, he said.
Fletcher was one of 50 officers policing the protest in 1984 when she was shot by gunfire from a first-floor window in the bureau.
According to the Met, the attackers used two firearms – a handgun and an automatic rifle. Ten protesters also sustained injuries from the attack.
In a statement today, police said they believed the incident was "part of the so-called 'stray dogs campaign' being orchestrated from Libya to attack overseas dissidents and their interests during that time".
The incident caused a breakdown in UK–Libyan relations, with armed British police surrounding the bureau for 11 days. Thirty bureau staff were eventually permitted to leave, and were later repatriated to Libya.
Although the Libyan government offered to pay Fletcher's family compensation in 1999, no Libyan official has ever been prosecuted over the incident.
Walton announced the Met police's "largest social media campaign" through targeted Facebook advertising to appeal for witnesses and participants at the demonstration.
"There were a number of witnesses who were part of the pro-Gaddafi counter demonstration, orchestrated from within the Libyan People's Bureau, whom we have never spoken to," he said, adding: "Allegiances change and we hope with the passage of time, witnesses who have not spoken to us will examine their consciences and come forward."
A £50,000 reward for information over Fletcher's murder has also been issued.
Fletcher's family responded to the news of the arrests with a statement on Thursday, the BBC reported:
Recently we have had to come to terms with another loss through the death of Yvonne's father, Tim.
His one regret in life was that no one had been arrested in connection with the murder of his daughter and never witnessed any justice.
Resolving this crime is still important to all the family.
Any information, however small, can help bring closure for the family and we therefore continue to support the Metropolitan police in their ongoing investigation.
Speaking from the Nicasa airbase in Cyprus, foreign secretary Philip Hammond said he was "delighted" the investigation had progressed.
"We have supported over many, many years the continued investigation into the murder of wpc Yvette Fletcher," he said.
"Obviously that has been difficult for much of that period because of the situation in Libya...I am delighted that the investigation has made progress."