William Gray Muir with the model of the proposed music school at the old Royal High. Picture: Ian Georgeson

But it has lain empty for decades and become the subject of a controversial tug-of-war to secure its future.

Hotel developers who have a lease on the old Royal High School still hope to overturn the council’s rejection of their plans – but they have a fierce rival in the shape of St Mary’s Music School.

Scotland’s only independent music school has won backing from city planning officials for its proposals and bosses there are so keen to show them off that they have developed a giant new model of how the school could look.

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It will be presented to councillors by the Royal High School Preservation Trust (RHSPT) when the St Mary’s planning application is debated next week.

As well as a 300-seat concert venue, it would boast two studio spaces and public gardens looking out over Holyrood Park.

RHSPT chairman William Gray Muir said: “One of the key things to remember about revamping existing buildings is that its original use is probably the most suitable one if you can find it.

“We want to split the function of the building with the public space accessed by a new entrance under the grand facade and the school accessed from the back, so we can have things going on simultaneously.

“I’d like to think of this as a school attached to a public concert venue rather than the other way around.”

The neo-Grecian building was designed by Thomas Hamilton in the early 19th century, serving as the school’s premises for over 125 years before being vacated in 1968.

The St Mary’s plans would see the former library and headmaster’s study converted into publicly available studio space, while the south-facing car park would be transformed, becoming publicly accessible gardens with room for performance space. However, Duddingston House Properties holds the contractual rights to the property, intending to base a new £75 million luxury hotel development on the Regent Road site.