A prolific sex offender who targeted children by masquerading as a caretaker will serve 18 years in prison, after an investigation by the Metropolitan Police presented indisputable forensic evidence.

David Pearce, now aged 70, from Cambridgeshire pleaded guilty to seven sex offences following the prosecution’s opening statement at Snaresbrook Crown Court on Wednesday, 6 May.

He was sentenced today, Friday, 3 July, at the same court.

In 1990, Pearce impersonated a caretaker and approached a group of four children at a lido in Barking, east London, pretending to search for lost keys. He lured them into a changing area before forcing them to strip off and inappropriately touching them under the false pretence of finding the keys.

The youngest was aged just eight years old.

After the incident, the children showed remarkable cognizance by running to a nearby police station to report the crime. This enabled officers to gather statements – helping build a picture of the offender – and allowed forensic officers to implement a cordon and avoid contamination of the scene.

Forensic officers discovered semen on a wooden bench within the changing cubicle and extracted a DNA profile, but it unfortunately did not match to anyone on the database.

As part of their enquiries, specialist officers took one of the children to a local gym to try and identify the offender, but there was no one present who matched the description of the suspect. After initial lines of enquiry were exhausted, the case was filed pending further investigative opportunities coming to light.

In 2019, Pearce was arrested for a separate offence of voyeurism. The DNA he provided was a one in a billion match to the suspect at the lido.

Upon obtaining this evidence, detectives reviewed similar reports and found victim statements from a 1996 incident which followed an alarmingly identical pattern of offending. Again, the 13-year-old victim said a man had forced her into shrubbery in a Barking park and assaulted her as he claimed to search for a pair of lost keys.

Not long after Pearce’s initial arrest in 2019, he was questioned in relation to the 1996 incident. The victim-survivor attended an identification parade, where she confirmed Pearce as the man who had assaulted her.

The concrete forensics and successful identification – bolstered by circumstantial evidence which showed Pearce living in the area in 1990 and owning a food truck situated close to the park in 1996 – provided detectives with enough to charge him.

Detective Constable Tony Anionwu from the Met’s Specialist Crime Unit said: “Pearce was a predator who disguised himself as someone in a position of trust to exploit and assault young children. His actions had a lasting impact, and I would like to thank the victim-survivors for their unwavering resilience and profound patience while we strived for justice.

“Our dedicated team of officers have handled this case with sensitivity. As a force we remain committed to securing justice for anyone who has experienced a sexual assault, no matter when they occurred, and over the past five years we have more than tripled arrests and charges for this crime.”

Forensic Scientist Bridget March, who was responsible for the DNA match in 2019, concluded: “Forensics play a key role in investigations, with our team of professionals meticulously examining items to locate and present evidence, backed by science. The advances in science and discovery of the match to Pearce’s DNA profile ultimately paved the way to secure admissible evidence.”

On Wednesday, 6 May Pearce denied a further four counts of indecent assault, six counts of attempting an act of indecency with a child and two counts of indecency with a child relating to 12 other children – all in the 1990s.

The prosecution chose to leave those charges on file after his guilty pleas were entered.

The Met has recorded significant year‑on‑year increases in reporting of sexual offences, suggesting more victims feel able to come forward. The Met is committed to improving victim experiences at every stage within an investigation, recently committing to a £10 million upgrade programme of the suites used to carry out video recorded interviews across its estates.