Jailing the 64-year-old, Judge Tom Gilbart told him: “This was quite shocking criminality by you. It was predatory behaviour which has had a significant impact.”

Riley, of Sandridge Close, Kearsley, appeared in the dock at Manchester Minshull Street Crown Court after pleading guilty to assault by penetration and two counts of sexual assault just days before his trial was due to start.

The court heard that the abuse began eight years ago when, on the first occasion, Riley sexually touched the woman after finding her asleep on a sofa.

“She then heard the defendant say, ‘I always knew you were a slag’,” said Mr Edwards, who added that the woman pushed Riley away asking him, “How could you do that?”

“Following that incident, the defendant made repeated suggestive comments to her,” said Mr Edwards

The woman did not inform anyone about the assault but the following year Riley sexually assaulted her once more and, on a third occasion, he again repeatedly touched her as she was sleeping.

“She describes the defendant’s conduct as relentless,” said Mr Edwards.

When confronted, Riley claimed he had been sleepwalking.

The woman eventually complained to police and Riley was arrested but initially denied the allegations against him.

Judge Gilbart sentenced Riley to four years and nine months in prison, placed him on the sex offenders’ register for life and barred him from working with children and vulnerable adults.