[2] The island was put up for sale in 1862 at which time Sir George Grey, newly commencing a second term as Governor of New Zealand, purchased it for £3,500.

[5] When Grey purchased the island, he was impressed with the building, commenting favourably on its thick walls, kauri timber and surrounding landscape.

He spent extravagantly on the property, filling the house with artifacts from around the world and importing rare plant and animal species for his gardens.

The island was a popular destination for tourists and day trippers from Auckland and for much of this time, Mansion House was operated as a hotel.

[8] In 1967, the last owner sold the house and surrounding land to the New Zealand Government so that it may be included in the newly established Hauraki Gulf Maritime Park.

[11] Originally administered by the Hauraki Gulf Maritime Park Board, it is now the responsibility of the Department of Conservation as part of the Kawau Island Historic Reserve.