Antoni Imiela, who is already serving seven life sentences, jailed for 12 years for rape of Sheila Jankowitz

A man dubbed the M25 rapist, who was jailed in 2004 for a series of attacks on victims as young as 10, has been found guilty of raping another woman in 1987.

Antoni Imiela, who is already serving seven life sentences, was given a further 12 years at the Old Bailey in London for the rape, indecent assault and buggery of Sheila Jankowitz. After the sentencing, detectives urged other potential victims to come forward.

Imiela grabbed Jankowitz near her south-east London flat in the early hours of Christmas Day, threatening to kill her if she called out and punching her repeatedly when she resisted.

Fourteen years later, he committed a series of rapes across the home counties which sparked the largest joint police inquiry since the hunt for the Yorkshire Ripper. All of his victims were strangers to him.

"It's likely that the police are unaware of all of his offending," said Detective Inspector John Foulkes, speaking outside the Old Bailey. "I appeal to the public, and in particular anyone who is a potential victim of his in the late 1980s or between 1996 and 2002, to come forward."

Imiela pounced on mother-of-two Jankowitz, who was then 31, near her flat in Forest Hill as she went to look for her husband after a row. She was later murdered in South Africa in 2006, but her original statement was read out in court in evidence.

Her mother-in-law, former husband and daughter all went through the ordeal of giving evidence after Imiela claimed that he had had consensual sex with Jankowitz, saying he "made love" to her.

Passing sentence, Judge John Bevan QC told him: "I find this case saddening, not only because Sheila Jankowitz's life was blighted from at least 1990 onwards by mental illness until her murder in 2006, but I also find your approach saddening, surprising as it may seem.

"I disagree with [prosecutor] Mr [Richard] Hearnden's suggestion that you hate women, on what I have heard in this trial ? you seem to me to have a dislike of humanity in general."

He went on: "You are wholly unrepentant about your life of guns, rape and general violence and, despite having served eight years of your life sentence, you have not expressed one jot of remorse."

Imiela was given seven life sentences in 2004 for his campaign of rapes, with a minimum term of eight years, making him eligible for parole earlier this month.

His victims included girls aged 10, 13 and 14, as well as women up to the age of 52, sparking widespread fear because of the randomness and geographic spread of his attacks and his willingness to strike in busy areas in broad daylight.

His sadism was epitomised by the fact he stole one victim's mobile phone and used it to taunt her mother about having raped her daughter.