FORMER council offices will have a luxury penthouse makeover after developers won an appeal.

Five-storey Priory House in Bartholomew Square, Brighton, will get an extra level after property agents gained planning consent for the extension at the third time of asking.

The city council sold the 25,000sqft property for £4.5 million in 2014 which property owners Barron Homes have recently converted into 40 flats.

Now after a protracted planning battle, a new 325sqm two-bedroom family home will be built on the city centre property, potentially adding more than £500,000 to its value.

Flats in the building, renamed The Green Diamond, are now coming on to the market with one-bedroom flats available for between £250,000 and £500,000.

One-bedroom flats for rent are being advertised at up to £1,300 per month.

The site is owned by West Acre UK Investments whose directors Michael and Nazila Blencowe also founded Barron Homes, which owns sites rented by Brighton and Hove City Council as temporary accommodation including Windsor Court.

The office building, which was built in the late 1980s, has been vacant since council staff left it in 2011 and its conversion to homes was allowed under permitted development rights despite a chronic shortage of high-quality office space in the city.

The plans had been knocked back twice by council officers who said the extension would cause significant harm to the historic character and appearance of the surrounding Old Town Conservation Area and neighbouring listed building Brighton Town Hall.

Stiles Harold Williams Planning, appointed to take the application to appeal following its second rejection, argued there was minimal impact to the views into Bartholomew Square which was outweighed by the public benefit of an additional family-sized home built on “a brownfield site in a highly sustainable location”.

SHW planner Harriet Nind said: “Given the housing shortfall in Brighton and Hove, it’s a great achievement to have rightfully justified the creation of an additional family-sized home in such a sustainable central location.”

Allowing the appeal, planning inspector Sheila Holden said the additional storey would be sufficiently set back to ensure that its visibility would be extremely limited.

SHW had argued that the additional storey to Priory House was far less significant than the 85ft high Skylight extension to Moshimo restaurant across the square granted planning permission in November.