The judge added that there seemed to be “little doubt” that the actions of the gunmen were “orchestrated and sanctioned” by Gaddafi, who “could not tolerate dissent or disagreement”.

The court had heard of the terrible trauma wrought on Mr Murray in witnessing the death of his friend and then having to attend the post-mortem. He and other officers had also suffered from guilt at what happened to her because she could have been sent away from the demonstration.

“No guilt should be felt by any of those police officers who survived the events,” said Mr Justice Spencer. “Nobody could have foreseen the cowardly shooting of a police officer in the back, and the sad fact is that Yvonne Fletcher was… simply in the wrong place at the wrong time.

“Rather than feel guilt, Mr Murray should feel proud of the way he conducted himself, along with his fellow officers, and of the way he did his duty.”

After the verdict, Mr Murray, from north-east London, thanked the judge. He said: “I do feel guilt for the murder of Yvonne, I don’t think that will ever go away. But I take comfort in the words of the judge. He has put my mind at rest, and we carry on.”

Outside the court, former colleagues queued to congratulate Mr Murray on his crusade. Neil Hayden, 58, who had been “puppy walked” by WPc Fletcher – trained by her – said: “She was a remarkable person. I never thought I would see this day. There have always been problems, always been obstacles, but John just kept going for 37 years. It is remarkable.”

Stephen Murphy, 64, who was with WPc Fletcher when she made her first arrest in 1977, said: “Everyone knows how much this means to John.” He had raised funds through charity rides and runs to help pay for a legal case, underpinned by the Police Federation.

Lesley Martin, 60, who worked with WPc Fletcher at Bow Street station, accompanied Mr Murray on the trip to the spot where she was killed. “Today has been a long time coming,” she said.

Asked how Mr Murray had continued against all the odds, she replied: “I can believe how he stuck with the case. He is just such a determined chap. I was in disbelief when the judge read out his ruling. Then that just turned to elation.”

The Government’s manifest interference with justice should be a source of shame

While she lay dying in his arms, PC John Murray promised his friend WPc Yvonne Fletcher that he would not rest until he brought her killers to justice. For the past 37 years, he has kept that promise, writes Matthew Jury.

On Tuesday, the first of those men, Saleh Ibrahim Mabrouk, was found responsible for WPc Fletcher’s murder by the High Court, but only because of Mr Murray’s tireless campaigning. 

Conversely and absurdly, four years ago the Government chose to intervene in Mabrouk’s prosecution, allowing him to walk free. If it hadn’t been for Mr Murray’s dedication to his friend and access to the civil courts, Mabrouk may have escaped justice altogether.