Headstone in memory of Police Constable Fletcher.

Police say they know who killed Police Constable Yvonne Fletcher in 1984 outside the Libyan embassy, yet they also concede that they can't take it to court because a trial presents a national security risk.

Scotland Yard gave a statement to the press on Monday, May 15, 2017, that they had the evidence needed to prove who murdered PC Fletcher but that they could not present it to a court.Police cannot charge anyone for PC Yvonne Fletcher's murder on the basis of "national security reasons." This means that her killers will escape justice.

The understanding is that the Home Office blocked the admission of a dossier of evidence.Saleh Ibrahim Mabrouk, the primary suspect, is an ex-minister of education of Colonel Muammar Gaddafi's regime.Gaddafi was arrested for involvement in the 1984 shooting.Police told Mabrouk that, "at this time," the case against him will not continue.

Mabrouk, a Libyan in his 50s, taught at a British university when he was arrested and held on grounds of a pending investigation into a conspiracy to commit murder.Now, his charges have been dropped, and he has been released from bail.

PC Fletcher's family expressed deep disappointment last night regarding Mabrouk's release.Fletcher was murdered while policing a demonstration in St.James's Square on April 17, 1984, just outside the Libyan embassy.

At the time, the shooting incited the unruly siege of the embassy prior to 30 of the occupants being abruptly deported to Libya, and it also resulted in the United Kingdom severing ties with Libya.Mabrouk was also deported following the murder, yet he came back in 2011 and sought political asylum.