David Orr of the Urbanist Group, who brought Harvey Nichols to Edinburgh and was the driving force behind the Mint Hotel Group, said the revamp of the old Royal High School on Calton Hill would open up the crumbling building to the wider community as well as guests.

The chairman of London-based firm, along with partner Duddingston House Properties, is this week holding a two-day public exhibition of potential plans before finalising proposals to go to Edinburgh City Council.

The joint developers want to turn Thomas Hamilton’s neoclassical building into a six-star hotel and have lined up market leaders to run the premises, which would create 680 jobs and generate around £27 million for the economy each year.

However heritage experts including Historic Scotland, the Architectural Society of Scotland and the Cockburn Association have raised concerns over aspects including the addition of windows and some planned buildings on the site around Hamilton’s centrepiece.

Mr Orr told the Herald he intends the hotel to be used by the community as well as clientele and there would be spaces specifically for outside use and in particular as a vehicle for arts projects.

He said changes to the buildings surrounding the school including the demolition of a jail and the building of St Andrew’s House meant the architect’s own original concept had changed over the years.

He said: “We think it is going back to the original vision of the design.

“There is recognition that some of the buildings that have been put up later have had an effect.

“It will be something that will give international opportunities and I think it will be good for the country.”

He said as a hotel its doors would be open to the public 24 hours a day. “It is designed to be populated.”

Susan Denyer, an adviser to Unesco, raised concerns over the wider cultural value of the project while Edinburgh conservation watchdog the Cockburn Association said that “an alternative use which is compatible with this unique A listed building within Edinburgh’s World Heritage Site should be brought forward”.

More than 300 attended a public meeting held by the AHSS in Edinburgh addressed by heritage experts.

The site is being leased to the developers by the city council, which it is thought would have to a significant amount to keep the structure from deteriorating further.

The proposals for the former boys’ school, which opened in 1829 but has been unused since 1968 when the school was relocated, are still being formed.

Mr Orr added: “We want to ensure the public has every chance to comment on our proposals to sensitively restore Hamilton’s masterpiece.”

More than half of the 580 visitors to an exhibition at the site completed a feedback questionnaire which revealed that 79 per cent of them were generally in favour of the redevelopment proposals, with over 75 per cent agreeing that a world-class hotel would be an appropriate use for the well-known Edinburgh landmark.

The exhibition is being held at the school on Thursday, March 5 and Friday, March 6 and everyone is welcome to attend.