A mentally ill man delusionally believed he was in a relationship with radio host Jackie O when he sent her hundreds of messages before showing up outside her home.

David Gourlay inundated the broadcaster with up to 2000 direct messages on Instagram over five months, many of which were sent consecutively and reflected her personal details.

Despite having never met the radio presenter – whose real name is Jacqueline Henderson – the 38-year-old wrote as if they had a pre-existing relationship and a child together.

Jackie O had feared for her family’s safety when a stranger had showed up near her house after flooding her with messages. (Tim Bauer)

“I am not giving up on us,” he vowed on July 3.

The co-host of the Kyle and Jackie O Show did not respond to any of the messages, some of which vulgarly detailed Gourlay’s sexual fantasies involving her.

The stalking escalated when Gourlay sent a bouquet of flowers – mistakenly addressed to “Jackie Anderson” – to her house.

Police found him sitting on a bench outside the radio host’s home in Sydney’s east and took him into custody before arranging a mental health assessment.

Gourlay – who has been diagnosed with schizoaffective disorder with bipolar – had delusions of being in a relationship with Henderson, his lawyer told Sydney’s Downing Centre Local Court today.

“He is battling quite a significant mental health issue,” Trudie Cameron explained during her client’s sentencing.

He had not been compliant with his medication and had reported suffering paranoia and hallucinations before sending the barrage of messages to Henderson, she said.

An expert report drew a direct correlation between his mental health and the offending because Gourlay’s actions arose out of his delusion, the court was told.

The co-host of the Kyle and Jackie O Show did not respond to any of the messages. (WireImage)

“When he’s medicated, when he’s well, he is a productive member of the community,” Cameron told the court.

She pushed for Gourlay to serve his sentence in the community, citing his genuine remorse for the offences and his insight into the fear it would have caused Henderson.

But the prosecutor pushed for the 38-year-old to be jailed over the “abhorrent” sexual messages in order to send a message to the community.

The facts didn’t make for pleasant reading, Deputy Chief Magistrate Theo Tsavdaridis agreed, pointing to the overly sexualised nature of some missives.

“The messages were targeted, unwanted and incessant,” he said.

He said Henderson had rightfully feared for her family’s safety when a stranger had showed up near her house after flooding her with messages.

Gourlay had an extensive criminal record and had been serving two community sentences at the time, Tsavdaridis noted.

He sentenced Gourlay to 16 months’ imprisonment, with at least eight months to be served behind bars.

With time served, the 38-year-old will be eligible for parole in March.

A five-year apprehended violence order prohibits him from approaching Henderson or contacting her except through a lawyer.

The order, which expires in 2030, bars Gourlay from assaulting, threatening, stalking or harassing the radio presenter or anyone with whom she had a domestic relationship.