A Milton Keynes pensioner has gone on trial accused of the “brutal” rape and murder of a teenage girl nearly 50 years ago.

Dennis McGrory, 74, was fuelled by rage when he sexually assaulted, stabbed and strangled 15-year-old Jacqui Montgomery in her home in Islington, north London in 1975, the Old Bailey heard.

Justice finally caught up with McGrory after swabs from Jacqui’s body produced a one-in-a-billion DNA match, jurors were told.

Opening his trial on Thursday, March 3, prosecutor Sarah Przybylska said: “Many years ago this defendant, when in his 20s, attacked, raped and brutally murdered the 15-year-old victim, Jacqueline Montgomery, in her own home when she was all alone.

“He was desperate at the time. He was trying to track down his ex-partner Josie Montgomery, who had recently left him, and he wanted to harm her.”

McGrory had become “wild with anger” after finding out at the end of May 1975 that his ex-partner – Jacqui’s aunt – was having an affair with a good friend of his, jurors heard.

The defendant, then 28, thought Jacqui would know where she was and he could force her to tell him, it was claimed.

The prosecutor said: “Whilst Jacqui may have known where she was, whether she ever told the defendant only he knows.

“No doubt furious with rage and wanting to attack Josie, the defendant took out his anger on the next best thing, Jacqui Montgomery, both raping and murdering her.”

During the attack, a page of Jacqui’s diary containing an address where her aunt had been was allegedly ripped out by the defendant.

Ms Przybylska said: “Whether in fact, as he was strangling Jacqui to extort an address, she fobbed him off, saying that was where Josie would be, we will never know.”

But the prosecutor suggested that the fact McGrory had the address was “damning evidence”.

Jacqui’s body was found by her father, Robert Montgomery, lying on the floor of their living room in Offord Road, Islington, in the early hours of June 2, 1975.

She had suffered fatal stab wounds as well as blunt force trauma to the face and been strangled with the flex of an iron.

Her skirt and jumper had been pulled up, consistent with a sexual assault, jurors heard.

A short time after the discovery, McGrory was spoken to by police and in interviews denied having anything to do with the murder.

Ms Przybylska told jurors: “Justice has now finally caught up with the defendant.”

As well as circumstantial evidence, new DNA evidence has “compellingly” established McGrory as the killer, she said.

Swabs from Jacqui’s body which found nothing relevant at the time have since linked to McGrory scientifically thanks to DNA advances, jurors heard.

Ms Przybylska said it was “at least one billion times more likely” that DNA from a vaginal swab included McGrory’s DNA.

She added there was evidence that McGrory had a sexual interest in Jacqui and had threatened to rape her.

“The evidence establishes that the defendant made good on his threat to rape Jacqui Montgomery,” Ms Przybylska said.

McGrory, of Milton Keynes, has denied charges of rape and murder.