Fridye had already served time for rape and three indecent assaults

The 77-year-old victim, who has since died, went to her grave never knowing if her attacker would be brought to justice, the Old Bailey was told.

But Carl Fridye, 32, was jailed for five-and-a-half years on Friday, after the case was re-opened by police.

Evidence gathered as part of the "cold case" inquiry was matched to Fridye through the national DNA database.

Forensic samples taken from the scene of the attack, in Islington in 1989, were frozen and stored in a laboratory for 12 years.

They were analysed again using a new technique during the cold case review last year.

"Advances in DNA techniques and analysis meant scientists were able to retest the sample that had been previously unidentified," said a police spokeswoman.

This case demonstrates that convictions are possible in cold cases even when the victim has died and can't give evidence in court Prosecutor Claire Ward

Fridye's fingerprints were also matched to a print found on the windowsill.

The court heard he climbed through the victim's window in the early hours of the morning and hit her in the face, sexually assaulted her and threatened to kill her.

Fridye, from Stirchley in Birmingham, had been addicted to crack cocaine at the time.

He later took a rehabilitation course while serving seven-and-a-half years for rape and three indecent assaults in Derbyshire.

Released in 2001, Fridye had since got a job and had been promoted to warehouse manager.

He wrote to the judge expressing remorse for his "despicable" behaviour.

But the judge told him: "You express sympathy and remorse - it is too late to express it to your victim.

"Despite the fact you were in front of a court on several occasions afterwards, you failed to show a degree of remorse when you could have done.

Victim left traumatised

"You failed to tell police there was another matter on your conscience."

Prosecutor Claire Ward said the victim had been left "very traumatised".