LONDON (Reuters) - A man arrested in 2015 in connection with the 1984 murder of a British policewoman outside the Libyan embassy in London has been released without charge because crucial evidence was not available for national security reasons, police said on Tuesday.
Yvonne Fletcher, who was 25, was hit in the back by a shot fired from the embassy while she was policing a demonstration by Libyan dissidents against Muammar Gaddafi, who then ruled the North African country.
London's Metropolitan Police force said officers believed they had identified those responsible for Fletcher's murder, but key material that would be needed for a case to be brought to court was not available for reasons of national security.
"I regret that we have not been able to deliver the justice that the victims and their families deserve," said Mark Rowley, the Met's assistant commissioner, referring to Fletcher and others who were injured in the incident.
The shooting of Fletcher triggered an 11-day siege of the embassy by the Met, the deportation of 30 Libyans in the embassy and the severing of diplomatic ties between London and Tripoli.
The shot that killed her was one of several fired from the embassy and 10 Libyan anti-Gaddafi campaigners suffered gunshot wounds. Police believe two weapons, a pistol and an automatic weapon were used in the incident.
The Met said the incident had been "an act of state-sponsored terrorism", part of a bombing and shooting campaign waged by the Gaddafi regime during the 1980s and 1990s, targeting Libyan dissidents in Britain and across Europe.
The man arrested in November 2015 in southeast England has not been named by police.
Fletcher's family said they were satisfied the Met had left no stone unturned in its pursuit of justice for her.
"We are deeply disappointed and frustrated that a prosecution cannot proceed at this time. We had hoped that the latest turn of events would finally lead to some closure for the family," they said in a statement.
The arrest of the murder suspect came as a result of new information obtained since the fall of Gaddafi in 2011, with London officers having made multiple visits to Libya since then.
The Met said the investigation would remain open, but that cases like this became harder to solve over time.
"Our judgment is that this concludes what was by far the best opportunity to solve this tragic case and provide a degree of closure for the victims and their families," it said.
Editing by Catherine Evans