Work is finally set to get under way to expand the Scottish National Gallery in Edinburgh.

The delayed scheme - set to cost more than first estimated at £22m - will see the gallery extended into Princes Street Gardens to create new exhibition spaces.

Large windows will run along the length of the venue, offering views of the capital.

The extension will also include a larger shop, cafe and restaurant for visitors.

Construction work will begin in October and is expected to be completed in 2021.

The gallery will remain open throughout the work, although some areas may be closed at certain times.

Bosses said the revamp would allow Scottish and international collections to be on show throughout the entire gallery for the first time.

Sir John Leighton, director-general of the National Galleries of Scotland, said: "This hugely exciting project will create the perfect showcase for the nation's extraordinary collection of Scottish art, giving it room to breathe and showing it off with real pride to the world.

"All will be welcome, whether to come in and immerse themselves in the romantic paintings of the Scottish Highlands, to take part in a family day or just to linger, enjoy the views and maybe pick up one of our sketch pads."