A “predator” who raped a teenager and murdered a woman whose bound and gagged body was found in a lake has been convicted decades after his “horrendous” crimes.

Serial attacker Donald Robertson was charged last year after a police cold case team found new DNA evidence linking him to the death of Shani Warren in April 1987.

The body of 26-year-old Ms Warren, who lived in Stoke Poges in Buckinghamshire, was found in Taplow Lake on the Easter weekend that year.

Donald Robertson
Donald Robertson (Thames Valley Police/PA)

Her car was abandoned in a layby on the A4, with bin bags containing remnants of grass from Ms Warren having recently mowed the lawn, and an Easter egg in the driver’s footwell.

Robertson, 66, did not attend his trial and the dock at Reading Crown Court was empty on Tuesday as a jury found him guilty of both crimes.

He was convicted of the false imprisonment, indecent assault and murder of Ms Warren between April 16 and 19 – her wrists having been tied with a car jump lead and ankles bound by a tow rope.

He was also found guilty of the kidnap and rape of a 16-year-old girl, who cannot be identified, on July 16 1981.

Police described “evil” Robertson as someone with a “long and horrific list of previous convictions” and said it is “a regret” there was not enough evidence at the time to charge him with the teenage girl’s rape in Farnham Lane, Slough.

Just days after being released by police in connection with that offence, Robertson raped a 14 year-old girl who had been riding her bicycle in Farnham Royal, a crime to which he pleaded guilty in October 1981.

Shani Warren's wrists had been tied with a car jump lead (Thames Valley Police/PA)
Shani Warren’s wrists had been tied with a car jump lead (Thames Valley Police/PA)

In a similar vein, less than two months after attacking and killing Ms Warren and only a few miles from Taplow Lake, he raped a 17-year-old girl who was walking home having missed the last train.

He is currently behind bars for that crime, having been convicted in 2010 after the incident was reviewed by the police’s cold case team.

The prosecution said new DNA evidence was the “cornerstone” of the latest case against Robertson – with traces matching his found on the underwear of both victims as well as on a mouth gag used on Ms Warren.

Police said they were sorry it had taken so long to bring her attacker to justice, but that the case coming to court was down to advancements in forensic science.

Thames Valley Police’s major crime review team’s principal investigator, Peter Beirne, told the PA news agency: “In relation to Shani’s family I’d like to thank them for their support, thank them for their patience.

“I’m sorry that it took so long to bring Robertson before the court, but we’ve only been able to do that as a result of advancements in forensic science. It was not as a result of any lack of effort on behalf of the police.

“It was just that unfortunately, at that time, there was not the evidence to enable us to charge Robertson.”

Mr Beirne branded Robertson an “evil and dangerous” man and a “predator” who had attacked women and girls “throughout his adult life”, subjecting them to “the most horrendous acts”.

He said Robertson’s failure to attend his trial “speaks volumes” to his character, labelling him “a coward, (who) wasn’t prepared to stand up and answer to the charges which were put before him”.

He praised the victim of the rape for her “strength of character” in going to court to give evidence during the trial.

He said: “I’d like to thank her for her bravery and courage in coming forward when we spoke to her, having to go through the ordeal of giving evidence before a crown court and also having to relive that horrific event which took place all those years ago.”

The victim said she can “finally get some closure” following the conviction, and thanked her family and officers for helping her pursue the case to justice as an adult.

“The weeks leading up to the trial have been very traumatic for myself and my family, but with their support I found the courage and strength that I didn’t have as a 16-year-old to pursue the case against the monster that put my life in turmoil,” she said.

She added: “Justice has been done and I can finally get some closure. So to anyone that finds themselves in a similar situation, don’t be afraid to ask for help, be strong and with your courage and the right support you will get through the trauma.”

Robertson did not give evidence in his defence, and his lawyer called no witnesses but claimed another convicted rapist guilty of crimes around that time involving tying women up and attacking them could have been the culprit.

Traces of DNA matching Robertson's was found on the underwear of both victims as well as on a mouth gag used on Shani Warren (Thames Valley Police/PA)
Traces of DNA matching Robertson’s was found on a mouth gag used on Shani Warren (Thames Valley Police/PA)

The jury took just seven hours and 18 minutes to convict Robertson of murder alongside the other charges against him.

Senior Crown prosecutor Robbie Weber, of the Crown Prosecution Service, hailed advances in forensic science leading to “new compelling DNA evidence clearly linking Robertson to both crimes”.

He added: “This evidence underpinned the case that we presented at trial which has today resulted in guilty verdicts.”

Robertson will be sentenced at Reading Crown Court on Thursday.

Mr Justice Wall, who presided over the trial, thanked jurors for deliberating on a “difficult and traumatic” case and told them he needed to consider whether to recommend Robertson is “never released” before passing sentence.