Mosman mansion feud heard in top court

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A neighbourhood feud in one of Sydney’s most affluent suburbs has escalated its way into the NSW Supreme Court following an alleged assault between the occupants of two harbourfront mansions.

Consultant Marie Barter launched legal action against her next-door neighbours commercial lawyer Joshua Theunissen and his wife Michelle as part of an “unfortunate” longstanding dispute centred around a shared terrace between the properties in Sydney’s lower north shore.

This week, the court heard how at one stage the Theunissens called police and told them that Ms Barter and her partner were “unlawfully” intruding the space and that Ms Barter’s partner had assaulted Ms Theunissen.

The alleged assault was just one of the events that led to both parties installing multiple cameras on the rooftop terrace in Mosman.

“Ms Barter installed the cameras to provide security for her property, and to record any unlawful incidents occurring on her property,” Justice Mark Richmond noted in his judgment.

“The Theunissens have also installed a CCTV camera which overlooks a large part of the roof terrace. Ms Theunissen’s evidence is that she feels a need to “monitor Ms Barter’s access to the terrace”.

Ms Barter launched the legal action with the aim of receiving a “declaration” that the Theunissens do not have exclusive possession or control of the terrace.

She is also seeking a declaration that the Theunissens are not allowed to have their BBQ, any tables and chairs, their son’s basketball hoop or any other permanent items on the terrace.

The two properties sit side-by-side on the same piece of land after being split into two lots in 1993.

Both properties are worth an estimated $3.38m each, according to

The debate comes due to the fact the Theunissens are able to access the terrace, which sits on the rooftop of Ms Barter’s property, through glass sliding doors at the front of their house.

However, Ms Barter is only able to access the terrace if she puts a ladder underneath a skylight which leads to the terrace.

“The defendants made various submissions regarding the design of Ms Barter’s house which, before the skylight was changed to be an openable skylight with an attachable ladder, did not have any means of accessing the rooftop,” Justice Richmond said in his judgment.

Ms Barter told the court how the Theunissens had attempted to prevent Ms Barter from accessing the terrace by placing netting over Ms Barter’s skylight.

“Ms Barter also objects to the Theunissens placing various items on the rooftop, including a basketball hoop, an 8-seater octagonal table, two decorative blue ceramic vases, other pot plants and two gas heaters,” the court heard.

“The Theunissens’ son plays basketball on her rooftop regularly which causes loud repetitive banging noises that Ms Barter hears throughout her house.

“Ms Barter also gave evidence that the Theunissens had frequently played loud music from the rooftop which prevented her from working in her office in her home and has generally disturbed her in her home.”

The court also heard how Ms Barter wished to have a declaration the Theunissens could not prevent or obstruct her from access or using parts of their shared driveway and garage areas.

In his judgment, Justice Richmond ruled in favour of Ms Barter stating that her use of the skylight did not “substantially interfere” with the Theunissens’ rights and use of the terrace.

However, he ruled that both parties’ CCTV cameras on the shared terrace was “actionable nuisance”.

“In the case of Ms Barter, the use of the camera is a substantial interference with the reasonable exercise by the Theunissens of their right to use the rooftop area for recreational purposes,” the judgment said.

“In the case of the Theunissens’ camera, it is a deliberate attempt to snoop on her privacy in using her property, the rooftop area.”

Legal costs between the two parties will be determined at a later court date.

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