The Ross Development Trust, the charitable trust behind the £25 million Quaich Project, said the development was now in “hibernation mode” and has signalled that it is ready to walk away from the project altogether.

Taking its name from the traditional Highland ‘sharing cup’, the Quaich Project was formed to take advantage of the topography of the land that forms West Princes Street Gardens, which closely mirrors the bowl of a typical quaich and, appropriately, the vision for the project aims to bring people together in new ways to celebrate one of Scotland’s finest green spaces.

However, in an interview in the Architects’ Journal, Trust chairman John Campbell QC revealed that Historic Environment Scotland (HES) warned it would object to the scale and impact of the revamp had the trust lodged a planning application.

Mr Campbell admitted that the project had effectively run out of money to take it forward any further and suggested it had also stalled due to opposition within the City of Edinburgh Council and HES.

John Campbell QC

He added: “I don’t have a queue of donors at my door saying ‘please take my money’. There’s nothing for them to donate to. There is no planning permission. There is no real finished product. There is just an idea. And now, particularly with Covid, fundraising is a nightmare.

“It is a great pity that it has come to nought. If you look for attributing responsibility for that, Covid has been a prime mover. But it is the city’s park and ultimately the responsibility has to lie with the council.”

John Campbell was appointed chair of the project in March last year following the resignation of Norman Springford in the wake of mounting criticism of its impact on the gardens.

A spokeswoman for HES confirmed it had warned that the proposed designs had “raised concerns of national interest”.

She added: “Although we are supportive of the garden’s facilities being improved, with the current proposals we noted we would object if an application came in.”

A council spokeswoman said: “We understand that the ongoing pandemic has meant that the Ross Development Trust have no funding to carry on activity, which is a great pity.

“We’re grateful for all of their work to date and we’re ready to resume the partnership if and when the trust gets back up and running again.”