THE former dedicated galleries of Scottish art, currently standing empty, shabby and cold beneath the National Gallery in the centre of Edinburgh, have long been a source of angst.

When Sir John Leighton became director general of the National Galleries of Scotland in 2006, he called the windowless, dingy display of art there an “apology” and was “deeply unhappy” about it.

He once referred to the concrete, subterranean galleries, opened in 1978, as “an enduring weakness.”

READ MORE: More details and images of the revamp at the Galleries

Now, 12 years later, and after at least one false start - and accompanied by a £5m rise in cost - the redevelopment of the National Gallery will begin next month, a three year project costing £22m, to be completed by 2021.

The project was put on a “pause” last March when the galleries’ first plan faced spiralling costs, many posed by the complex site: on a man made hill, in a major public park, under an A-listed building and above one of Scotland’s major railway lines.

Now the galleries (NGS) have unveiled a new conception of the revamp, which will create new galleries for the display of Scottish art, and a complete rehang of the entire gallery space.

The changes from the first plan mean that the new gallery spaces will stay not extend the facade five metres into East Princes Street Gardens, as previously planned, although it will feature a newly revamped entrance and pathways.

Sir John said he is confident that more than £10m in funding, yet to be announced, can be secured.

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He said: “What we have now is fully contracted price, and if we had pressed ahead with the original scheme, it would have been considerably more than £22m.

“So we took the difficult decision to revise the project and recast it, and personally I think what we have now is a stronger concept.”

Sir John added: “The rest of the cost comes from fundraising, and we have a substantial amount of that already, so I am confident that will be able to raise that. There is a significant amount in already, and there is somewhere to go.”

He added that he was “very confident” the project would be completed on budget.

Work will begin in October, and the NGS say that the galleries will remain open throughout the redevelopment project.

However, to enable excavation works to the galleries directly beneath, the notable Playfair Steps, at the rear of the National Gallery, will be closed for the duration of the building work.

The Playfair Steps, designed by William Henry Playfair, are an historic steep flight of steps from the Mound to Market Street.

For the next two years the traders who work in the route to the Playfair steps during the Festival will not be present.

The new galleries, with six large windows running the length of the new Princes Street Gardens facade, will have a “broader” look at Scottish art.

READ MORE: How the 'pause' in revamp was revealed in 2017

They will feature the art of Allan Ramsay, Gavin Hamilton and Sir David Wilkie, as well as 20th century artists such as Charles Rennie Mackintosh, Stanley Cursiter, Raeburn and the Scottish Colourists Peploe and Cadell.

The plan will involve “extensive new landscaping in the gardens”, a large lift for art and people, as well as a larger shop, and a new cafe.

The galleries say that once open, they will have a “dedicate family day” one day a week, and more volunteers working in the galleries.

The first sign of the revamp will be construction work in October, with new steps and paths by next spring.

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Funds announced for the revamp are from the National Lottery, worth £4.9m, and the Scottish Government, worth £5.5m.

Dr Tricia Allerston, co-director of the Scottish National Gallery Project, said visitor numbers to the gallery have almost “doubled in the past ten years but fewer than one in six of them made their way to the cramped, dark spaces which used to house the national collection of Scottish art.”

She added: “Visitors will be able easily to discover, appreciate and enjoy our highly significant collections of Scottish art through a series of displays designed expressly to engage them.”