A friend of policewoman Yvonne Fletcher who was murdered outside the Libyan embassy in 1984 has launched High Court action in a bid to finally unmask her killers.

John Murray, who cradled the 25-year-old as she lay dying, is making a civil claim for a nominal amount of £1 against a former aide to Libyan leader Colonel Muammar Gaddafi.

The retired police officer aims to get Saleh Ibrahim Mabrouk to give evidence in court and reveal who was responsible.

Mr Murray’s lawyers also hope to get key material that was previously kept secret for national security reasons presented in court for the first time.

He said: “The main thing is to make that evidence public and make people realise what that evidence contains. I think once that evidence is made public people will be shocked.”

Mabrouk, who denies wrongdoing, was arrested on suspicion of murder in 2015 but two years later the Metropolitan Police said that, while detectives could identify those responsible, charges could not be brought.

This was because crucial evidence had been kept secret to protect national security.

At the time of his arrest, his son, Osama Saleh Ibrahim, told the Guardian that his father “didn’t do anything”.

A still taken from video footage showing a demonstration outside the Libyan Embassy in London shortly before Pc Yvonne Fletcher was shot (Metropolitan Police/PA)

Mabrouk was inside the Libyan embassy on April 17 1984 when a gunman opened fire from inside the building as both anti- and pro-Gaddafi demonstrators gathered outside.

Pc Fletcher was fatally shot and Mr Murray promised her as she lay dying that he would find her killers.

His lawyer, Matthew Jury, from McCue & Partners, said: “On behalf of all those who loved and knew Yvonne, John wants to fulfil the promise he gave to her before she died – to bring the suspects to justice. These proceedings may be the last hope and chance to do so.”

Mr Murray is appealing for public donations to fund his legal battle athttps://www.crowdjustice.com/case/wpc-fletcher/

In memory of WPC Yvonne Fletcher pic.twitter.com/SE1UluaHOp — Metropolitan Police (@metpoliceuk) April 17, 2019

On Wednesday, Metropolitan Police Commissioner Cressida Dick laid a wreath at the memorial to Pc Fletcher, 35 years since she was killed.

The Scotland Yard chief said: “I was a young officer in the Met 35 years ago when Yvonne was shot. In 1984 I worked from West End Central – just half a mile from St James’ Square.

“That terrible event shook all of us who were in the Met at that time. All these years later there may be fewer people who directly experienced the impact of those events still in the Met, but as a police family we still collectively feel her loss.

“Today we mark her death and remember the contribution she made as a valued colleague and as a police woman, dedicated to the public, and we think of her family.”

The force said the investigation in to her death remains open and it is “absolutely committed to bringing justice to her and her family”.