The mother of a teenage Royal Navy sailor who vanished 40 years ago has called for a “serial killer” suspected of murdering him to finally reveal where her son’s body is hidden.Speaking as Simon Parkes’ suspected murderer, the former navy petty officer Allan Grimson, was sentenced for sexual offences against four boys and men, Margaret Parkes, 80, said time was running out for her and her 84-year-old husband, David, to find out what happened to their son.She said they had not been able to hold a funeral and the not knowing had hung over the family for four decades. “It never goes away, it never will. It’s affected our lives tremendously.

I think we’re totally different people to how we were before it happened,” she said.They still hope their son’s remains may be found. “That’s what keeps you going, that you will know,” she said. “Whether Grimson will admit it, I’m very doubtful. I would like it to happen but I doubt it.

I think it’s something to do with power, maybe. I try not to think of him as a person, I just think of the victims.”Parkes, a retired primary school teacher, said she felt Grimson, 67, should never be released. “He should be kept in for ever.

He shouldn’t be in the community. He shouldn’t be let out on parole.

He’s not going to change.”Grimson has been in jail for more than 25 years after admitting killing two young men, both of whom had been in the navy in the late 1990s in Portsmouth. The sentencing judge in 2001 described him as a “serial killer in nature if not by number”.In July this year, Grimson was convicted by a jury of sexual offences against four boys and men, the youngest only 14, also in the 1990s, and on Friday the judge Paul Dugdale jailed him for another 22 years for these crimes.The judge told Grimson: “You remain dangerous.

You still pose a significant risk to members of the public.”He said Grimson had targeted vulnerable boys and young men whose trust he had abused. They had suffered “lifelong” harm, the judge said as he praised their “staggering courage” in coming forward now.Dugdale said Grimson would not be eligible to be considered for parole until just before his 80th birthday, but added that his life sentence for the two murders meant he may never be freed.

Allan Grimson in 2001. He is now 67 and has been in jail for more than 25 years.

Photograph: PAMargaret Parkes followed the trial in the summer from her home near Bristol. Her son’s disappearance was mentioned during legal argument when Dugdale acknowledged that Grimson was a suspect.She was impressed by the four men who gave evidence against Grimson. “They’ve come forward after all these years and they’ve been traumatised all their lives and to go through a court case it must have been dreadful, but so important to them.

You can’t bring back what he’s taken away,” she said.Her son vanished in Gibraltar on 12 December 1986 when the ship he was serving on docked in the British overseas territory. He has never been found.

Grimson, who was serving on the same vessel, has long been suspected of killing Simon, though he denies it.Parkes said her son had been looking forward to getting back to England and was going to be posted at a navy air station in Somerset. “He was just a youngster – 18, well, almost 19. He was liked by everyone.

He was just fun. He enjoyed life,” she said.“When he disappeared it was dreadful, such a shock.

You just went into automatic mode really. All we had was a phone call.

The navy said that he’d gone awol. We had about 10 or 12 years of not having any support or any contact with anyone.

We’re just ordinary people. We didn’t know how to deal with authority.

The press were the only ones that every now and again would bring it up.”A family photograph of Simon Parkes and his mother in the garden of their home. Photograph: Martin Godwin/The GuardianIn 1999, Grimson led British police to the bodies of Nicholas Wright, 18, and Sion Jenkins, 20, whom he had murdered in Hampshire on the same date – 12 December – in successive years, 1997 and 1998.Parkes said: “The police came and said they were looking back because it was 12 December he killed them and Simon disappeared on the 12th, so that was the link to begin with.”Over the years, there have been searches in Gibraltar but Simon’s remains could not be not found.

It means the family have not been able to obtain a death certificate.In 2020, the Parole Board recommended Grimson be moved to an open prison to prepare him for freedom. “He was very, very close to being released,” Parkes said. “We couldn’t believe it but were helpless to do anything.”His chance of liberty was scuppered when the four men came forward to describe the offences Grimson had committed against them between 1994 and 1999.Parkes once asked Grimson directly what happened to her son. “I did write him a letter when he was in prison, years and years and years ago. But nothing came of that,” she said.She was still struck by Grimson telling police when he was arrested for the murders of Wright and Jenkins that killing was “better than sex”.

She said: “You can’t change that mentality in a person. I think he’s tried to be a very good boy in prison, a model prisoner probably, but I think he should stay in for as long as possible.”There is another chance for the family.

An inquest for Simon is finally due to be held in Gibraltar next year after a campaign by a local journalist, Ros Astengo, who is writing a book about his case.Parkes and her husband have health issues. She said: “We’ll go over if we can manage it.”Does she think she will find the answer to what happened there? “Who knows?” she said. “It’s taken such a long time to get to this point.

We might not be here next year.”