A gardener who raped a teenager and sexually assaulted her two friends in a disused Plaistow building more than 25 years ago has been jailed.

William McMahon, 60, of no fixed abode, was sentenced on Friday to 18 years and two months for the attacks.

Snaresbrook Crown Court heard how the three girls, two aged 13 and one aged 12, were targeted as they played together near the Upper Road section of The Greenway on the evening of June 29, 1990.

They went inside the derelict building to look around, but were followed by McMahon, who threatened them and forced them to remove their clothes.

He then raped one of the girls before going on to sexually assault her friends.

Although forensic evidence was taken after being reported to police at the time, nobody was ever caught and one of the girls died before anyone could be brought to justice.

The case was reviewed in 2010 and in April last year, McMahon was finally identified after being arrested for an unrelated matter.

On Monday, April 25, the first day of his trial, McMahon pleaded guilty to one count of rape, three counts of indecent assault and three counts of false imprisonment.

Det Insp Keith Braithwaite said: “McMahon stole the childhoods of his victims, causing them extreme distress and pain throughout their lives - which continues to this day.

“Perversely, McMahon continued with his life as normal for over 25 years.

“I would like to commend the victims for their courage and determination in pursuing this conviction and hope today’s sentence goes some way to bring closure to them and their families for McMahon’s heinous crimes.”

Catherine Wear, the reviewing lawyer for the Crown Prosecution Service, added: “The defendant trapped the girls in the abandoned building, telling them to face the wall.

“He did everything he could to disguise his identity, including making the girls put their clothes over their heads and giving them false information about himself. This made it very difficult for the police to identify him at the time of the attack.

“Through painstaking police work and a strong prosecution case justice has at last been done.”

Officers believe McMahon may have also targeted other people and ask anyone with information to call 020 8217 6538 or Crimestoppers anonymously on 0800 555 111.