It was purely just 'Google luck'," says Warren Au of how he came to work on this home in Sydney's Mosman. Warren, the director of Studio Gestalt, was surprised to receive an enquiry email from the owners.

"I looked up the real estate pics and thought, 'You've got to be kidding.' I thought someone was pulling my leg," he says. "But I gave them a call and it was actually a real client, with a real project. I struck gold."

Gobsmacked, Warren's first port of call was to his friend and fellow designer Alex Mason of Studio aem. With a philosophy of two is better than one, the pair – who first met as graduates working at the same firm – embarked on the project together.

Sitting on , the architectural envelope didn't require any structural work. Inside, however, the house called for a whole new reinvigorated identity.

The scope, initially joinery specifications and a comprehensive furniture package, ballooned to encompass accessories, lighting, art and soft furnishings.

"The original house was executed to a high standard through original selections and construction, so we were lucky in that we had a strong aesthetic foundation that was high quality – it provided us with a good base," says Alex. "The intention was to complement what was existing and make improvements with ."

In particular, all the carpeting was removed and replaced with elegant, in an effort to "add to the traditional element of the home", says Alex.

Broadly, the concept involved harmoniously such as the traditional fireplaces and decorative French windows with panoramic views across Sydney Harbour.

Due to the vast, expansive nature of the floor plan, Alex and Warren wanted to create visually contained spaces not necessarily closed off by doors or partitions, but distinguished by a composition of furniture and demarcated by rugs and lighting.

Experienced in hospitality design, especially big restaurant venues, Warren was familiar with this type of division and allotment. "I'm used to creating fit-for-purpose spaces, especially smaller defined pockets, which is what we have done here," he says.

On the ground floor, the west wing has been carved into three zones: a dining table with a silk rug underfoot, with Baxter's 'Chester Moon' sofa and occasional chairs surrounding a set of coffee tables, and an arrangement of Gubi's 'Pacha' chairs.

The east wing comprises a TV room and playroom with casual meals and dining. The and extended with a Super White dolomite island.

Behind, there's another full working Chinese scullery with Caesarstone bench. "It was designed to be the absolute workhorse of the house," says Warren.

Floor-to-ceiling cabinetry in rich chocolate Eveneer timber veneer hides fully integrated services. "From a holistic perspective, we wanted to maintain similar silhouettes and materials for the joinery throughout," says Warren, referencing the same design, elevated with bronze detailing, that has been used in the master bathroom and with a chest of drawers and extensive storage hidden behind a fluted sliding door.

A light touch was applied to all seven bathrooms, but , which has been completely reorganised and lined in handmade tiles. Having undergone the most extensive changes, the by way of round-edged double vanities, halo-style pendants and arched mirrors.

The adjacent master bedroom has been treated as a true suite, with an , ottoman and armchairs.

"Even though the house has so many large living spaces, this provides uninterrupted quiet and retreat," explains Warren. Another four bedrooms are clustered on this level in addition to a sweeping terrace.

All three levels are linked by which unfolds into a foyer on the lower-ground floor with a glass-topped B&B Italia 'Bolt' entrance table by Mario Bellini.

Through a floor-to-ceiling internal glass pane is a view to the palatial study, where there's both a desk and a B&B Italia 'Tufty-Time' sofa by Patricia Urquiola which, in its bone and navy colour, was selected as a hero piece to cap off this fine home.