The mixed-use development, called Sunnyside Park, will see the former Sunnyside Royal Hospital site in Hillside transformed into housing, retail, commercial development with social housing including affordable, retirement and assisted-living housing in a mixture of apartments and family homes.

Sunnyside Royal Hospital in Hillside closed in 2011 after serving as a mental health centre in rural Angus for 153 years. The site was acquired by Montrose-based Pert Bruce Construction Ltd and Edinburgh based FM Group, under the banner of Sunnyside Estates, from NHS Tayside in a seven figure deal.

The new owners applied for planning permission to build 265 homes in and around the B-listed main buildings having already received permission by Angus Council to demolish eight listed buildings to make way for retirement, supported and affordable housing.

But Historic Environment Scotland has objected to its proposals to level six listed buildings in addition to the likes of the former admin block and chapel.

The government heritage agency said blanket moves to demolish the B-listed nursing accommodation Booth House, fire station, water tank and workshops is “of much more concern”.

“This is the focus of our objection,” said case manager Ian Thomson.

“We welcome the stated commitment to retaining and re-using the Main Building, Hospital Building and Carnegie House, together with their ancillary cricket pavilions and summerhouse.

“However, it would have been helpful if more detailed discussion on the handling of the conversion (even as potential indicative schemes) could have taken place in parallel with these demolition proposals.

“This would have given us more confidence that the loss of certain buildings would allow and enable the retention of others.

“However, this is a discussion which can hopefully take place now.”

Sunnyside Estates completed a justification survey which sought “agreement in principle” from HES to retain the three “primary” buildings.

“All three buildings would be restored allowing the retention and cultural heritage to be preserved and appreciated, and to be utilised and enjoyed by future generations,” it said.

“The high costs associated with the restoration of these fabulous examples of local heritage unfortunately necessitate the sacrifice of other existing buildings.”

David Stewart, director of Sunnyside Estate, added: “Our vision is for a distinctive development which enhances and benefits the local area, sustaining and creating local jobs, has been foremost in our thinking for Sunnyside.”

The development plan indicates the release of around 265 houses, with 140 in the first phase period to 2021, with the remainder to follow within five years.