Originally called Craigdarragh House. It was built in about 1850 for Francis Gordon, to a design by Charles Lanyon.
This is from the estate agents details -
During WW2 the house was commandeered by the Army and a large hutted encampment was constructed in the grounds and housed some of the first American troops in Europe. Later the camp was used to house German prisoners of war. After the death of Major Workman the house was sold to the Sisters of Mercy and converted into a nursing home for the elderly, St.Columbanus nursing home, in the 1950’s. The nursing home was closed in 2002. Following the acquisition of the house by a local consortium after the home closed, a number of schemes were considered to develop the grounds and use the proceeds to restore the house. After considerable consultations, a decision was made by The Planning Appeals Commission in June 2006 granting planning permission to construct 5 substantial dwellings to the eastern end of the house to provide the required proceeds to restore Craigdarragh to its former glory. This scheme remains unfulfilled.
This is from BBC News in 2010 and seems to partially contradict the above -
Planners have rejected a proposal to convert a listed building, on one of NI's most exclusive roads into a house.
The plan, by Newtownards firm R&A Developments, would have involved converting St Columbanus nursing home.
It would also have led to five new houses in part of the grounds at Craigdarragh Road in Helens Bay.
Planners blocked the development because visibility from the driveway to the main road was so poor it was deemed to be an unacceptable road safety risk.
It was sold for around £2m sometime after 2015