IT has been described as one of the most exceptional collections of Scottish Colourist works,

Now a treasure trove of works by George Leslie Hunter, Samuel Peploe, FCB Cadell and JD Fergusson are to be sold for an estimated £3m.

The Harrison Collection was formed in the 1920s and 1930s by Major Ion Harrison, a patron and close friend of the artists.

It contains 31 works, and will be sold on June 12 at Sotheby's, the auction house, as part of their Modern British art sales.

Passed down through the family, the works remained together at Croft House in Helensburgh, Major Harrison’s home, and is currently being shown at Glasgow Art Club, and then, later this week, at Edinburgh's Tattoo offices in Cockburn Street.

The White Room by Cadell, an oil on canvas from 1915 has an estimated price of up to £500,000, while Cadell's Reflection from has an estimate of up to £600,000.

Peploe's Michaelmas Daisies and Oranges, meanwhile, could also sell for half a million pounds.

Thomas Podd, Sotheby’s Scottish Art Specialist, said: “Visiting Croft House for the first time was an experience that will live long in the memory. "Crossing the threshold and walking into the elegant reception hall, one was greeted with Cadell’s masterpiece ‘The White Room’ and its harmonious tones of white and grey punctuated with flashes of dazzling colour.

"Through the hallway, lined with watercolours by Hunter filled with Provençal warmth, and into drawing room, one’s eye was instantly drawn to Cadell’s ‘The Drawing Room, Croft House’, hanging in the very same room it depicts, with the majority of furniture and artworks unchanged some eighty years later.

"It is hard to imagine a work that encapsulates so perfectly the spirit of an entire collection."

Major Ion R. Harrison was Glasgow ship owner who first encountered the work of the Colourist artists in 1921 when, encouraged by his friend Dr Thomas Honeyman, later director of Glasgow's art galleries, he attended an exhibition at ‘Alex. Reid & Lefevre’ on West Street in Glasgow of paintings by Peploe.

Harrison purchased his first work by Peploe three years later, followed by a number of paintings by Hunter.

Not long after Harrison purchased his first painting by Cadell, The Pink Azaleas.

The Colourists term describes the work of Cadell, Fergusson, Peploe and Hunter, but it was coined in 1948 when three of the four were already dead.

They were all inspired by French painting, and in 1924, they exhibited their works together for the first time, in an exhibition entitled Les Peintres de l’Ecosse Moderne at the Galerie Barbazanges in Paris.