Prisoner star Maggie Kirkpatrick has had her historic sexual assault conviction and sentence overturned following a successful appeal in the Victorian County Court this morning.

Kirkpatrick, who is best known for her portrayal of the character Joan "The Freak" Ferguson in the classic TV soap, was found guilty in August of two counts of indecent assault and one charge of committing a gross act with a person under 16.

The 74-year-old was sentenced to an 18-month Community Corrections Order for the assault of the girl, who was aged 14 at the time.

Her portrayal of "The Freak" made her a household name in Australia and won her scores of fans like the 14-year-old girl from Melbourne.

In 1984, the girl was a patient at a psychiatric hospital where she befriended a woman who also worked on the show, who introduced her to Kirkpatrick.

The court was told the actress collected her fan from the hospital and cooked her dinner.

Then they watched television before going to Kirkpatrick's bedroom where the actress allegedly sexually abused the girl.

When the allegations were aired in July, Kirkpatrick said they were malicious and untrue, however Magistrate Peter Mealy ruled the victim's testimony as truthful.

Kirkpatrick was found guilty in August and set to be placed on the sex offenders register for eight years and undergo treatment programs.

The stage and screen actor yesterday entered the witness box and denied any wrongdoing, and told the judge she did not molest the girl.

Today Judge Geoffrey Chettle said Kirkpatrick should not have been convicted in the Melbourne Magistrates' Court and dismissed the conviction against her.

This is a breaking news article. More information will be added as it comes to hand.