Four buyers were involved in pre-auction negotiations for the property at 26 Olphert Avenue, and an overseas buyer won after paying $18 million.

This exceeded initial expectations that the mansion would sell for $16 million and beat the previous sale price of $4 million in 2021.

The mansion has undergone extensive renovations over the past few years, with the seller divesting the property outright.

The sellers are a London family who stayed abroad for work; Hamptons-style renovations were implemented throughout the property, adding a sense of luxury to its indoor and outdoor spaces.

Features of the property include an infrared sauna, a cinema room, a games room, a wine cellar and a gym.

The property also has a self-contained one-bedroom apartment with private access to the street.

Adam Reichman, lead agent from Ray White Double Bay, said buyers were attracted by the mansion's finishes, location overlooking the harbor and ownership of the 942-square-meter lot from north to south.

"It was a great result for a highly competitive property, and we saw 92 groups walk through the home throughout the event.

"This is a well-built home that is attracting families and local and overseas buyers.

"There are not many turnkey properties of this type on the market in Vaucluse at the moment."

When you count the self-contained apartment for guests or au pairs, the house has six bedrooms, in addition to four bathrooms.

Located 20 minutes from the central business district, it also has landscaped gardens, an integrated sound system and several outdoor entertainment spaces.

The median home price in Vaucluse has remained stable over the past 12 months, with an average purchase cost of $837,500.