IT is one of Scotland's most loved theatrical venues, which for more than a century has been enthralling audiences with festival shows, musicals, dramas, and its popular annual pantomimes.

But the King's Theatre in Edinburgh is also, in the candid words of its famous honorary patron, the actor Brian Cox, "sh*tty" in its backstage areas, and in need of a major and perhaps overdue revamp.

The old, but still resplendent theatre, which was yesterday described as being like a "warm hug" to its audiences, is in need of some, expensive, Tender Loving Care itself, its operators said.

The £20m to £25m redevelopment plan for the King's Theatre in Edinburgh was officially launched yesterday, with new visualisations of how the revamp will radically change the appearance of the theatre, inside and out.

The revamp of the theatre, which opened in 1906, will see it closed between September 2021 and early summer of 2023.

READ MORE: The revamp of Edinburgh's King's Theatre

It will therefore not be available as a venue for the Edinburgh International Festival, for which it is a mainstay, in 2022, and two seasons of pantomimes will be moved to the Festival Theatre.

As part of the plan by its operators Capital Theatres, there will be a new glass-walled roof area, providing views over the city, new access plans, and the upper tier of seats will be altered, although the rococo splendour of its main auditorium, with its ceiling mural by John Byrne, will see little change.

The architects for the project will be Bennetts Associates, which is also working on the revamp of the Citizens Theatre in Glasgow.

Capital Theatres have raised £9m towards the total thus far: they will now try and raise funds from the Heritage Lottery Fund, foundations and charitable trusts to revitalise the theatre, which attracts 200,000 people a year.

Dame Joan Stringer, chair of Capital Theatre, said: "It is one of the handful of Grade-A listed theatre buildings in the country which has yet to have a refurbishment.

"It is badly in need of major refurbishment, and without that investment, and our stewardship, audiences and performance will decline, and it would be at real risk of closure, either because of a collapse of infrastructure or because audiences would decline - we must not let that happen."

Changes to the stage, backstage areas and orchestra pit will "re-invigorate the artistic programme", she said.

READ MORE: How we reported the King's revamp plans last year

The trust believe that the dilapidated and old-fashioned state of the theatre's backstage and technical areas has led to a decline in the quality of the shows appearing there on tour.

The plan, the trust said, will lead to a doubling in opening hours, and will increase annual visitor figures by 50%.

New additions to the theatre will include a new cafe and bar, as well as the rooftop "hospitality space."

There will be new lifts and ramps, to improve accessibility, and an education space created from the old billiard room.

The stage will be flattened to attract touring opera and dance shows and back of house facilities - dressing rooms, wardrobe and the green room - will be given a "long overdue" facelift.

Duncan Hendry, chief executive of Capital Theatres said that the changes will "widen the theatre's repertoire and rejuvenate the theatre."

Mr Hendry noted the backstage areas and the orchestra pit, in particular, were in great need of upgrading.

He added: "The King’s Theatre holds a special place in the hearts of many people from Edinburgh and further afield.

"In early 2019 we will provide ways in which people can engage with, give opinion and support the project."

READ MORE: Brian Cox on the impact of the V&A on Dundee

Supporters of the theatre plans include Mr Cox, who spoke at length about his regard for the theatre yesterday.

He added: "The King’s Theatre is a gem which deserves to be preserved.

"If we don’t invest in our theatres, we stand to lose a vital part of Scotland’s cultural heritage and a theatre for everyone for generations to come."

Ian Rankin, the author, said: "I always enjoy my visits to the King's Theatre. It's a grand space where magic happens for all age groups.

"But like other buildings of its vintage, it would benefit from a bit of TLC, bringing it up to scratch for the twenty-first century. This is our chance to shape the King's for future generations. It's too good an opportunity to miss and I hope fans of the theatre from Edinburgh and beyond will join in."