More than two dozen sketches by the 18th-century master Thomas Gainsborough have been discovered at Windsor Castle after going unnoticed in the portfolio of another artist for more than 100 years.



Some 26 drawings, most of which are landscapes, by the renowned painter were found within an album in the Royal Collection created in the 19th century and credited to Sir Edwin Landseer, one of Queen Victoria’s favourite artists.

Leading art historians Lindsay Stainton and James Hamilton now say that they were wrongly attributed and are actually early works by Gainsborough, known for his lifelike portraits and British country landscapes.

Rosie Razzall, the Royal Collection’s curator of prints and drawings, told the Guardian: “We’re really excited by this discovery … If it means we have 26 early drawings in the collection, that’s really significant.”

The black-and-white chalk drawings – vivid depictions of landscapes around Sudbury, Gainsborough’s birthplace in Suffolk – have never been published or exhibited before. The collection is drawing up plans to show them for the first time.

One of the studies relates to a famous 1748 Gainsborough painting in the National Gallery, titled Cornard Wood, Near Sudbury, Suffolk. Another may be a composition for a lost and previously unknown picture.

Cornard Wood, Near Sudbury, Suffolk. Photograph: National Portrait Gallery London

His hand in the works was first spotted by Stainton, formerly of the British Museum and a noted Gainsborough specialist. On a visit to Windsor Castle, she was examining a number of works, including the album, and recognised his style immediately. She described it as a fascinating discovery, and said: “It’s exciting that Windsor has suddenly got 26 more drawings by Gainsborough.”

Hamilton will include the discovery in his book, Gainsborough: A Portrait, to be published on 10 August by Weidenfeld & Nicolson. . He said that relatively few of Gainsborough’s early landscape drawings have survived and the new finds reveal him “at his most inquisitive and energetic”.

Both Stainton and Hamilton point out that one particular drawing has deliberate sharp folds and a little oil mark – just like one in the British Museum, which is definitely by Gainsborough.

Thomas Gainsborough, Study for ‘Cornard Wood’, c. 1748. Photograph: Royal Collection Trust

Hamilton said: “This is undoubtedly a group of drawings by Gainsborough and extremely exciting.”

The drawing for Cornard Wood is “an important and highly revealing squared-up study”, he said. “Squaring-up” a drawing was a common way for artists to transfer a composition to a painting. Stainton said that when the drawing is superimposed on to the painting they were “a perfect match”.

It also confirms the attribution of an oil sketch which previously belonged to the dealer Philip Mould and “which at the time no one took seriously as being a preparatory study for Cornard Wood”, she said.

“But I can now establish that the drawing and the oil sketch are both studies for this famous painting in the National Gallery.”

The misattribution to Landseer was responsible for the collection being overlooked. Landseer painted royal animals and Scottish subjects, including his monumental The Monarch of the Glen, and guided Queen Victoria in her own etchings.

After his death in 1873, the queen asked his executors whether the Royal Library could acquire some of his sketches. They offered this group, “which the Queen liked,” the Royal Archives record. They were then mounted up in a heavy album headed Sketches of Sir E Landseer.

In 1995, after Stainton saw some initial photographs, the Royal Collection reconsidered them, cataloguing them as “from the circle of Thomas Gainsborough or the Norwich school”. But it was only recently that she was able to look at them properly.

She said: “The executors thought they were by Landseer as they were from his studio. One of the mysteries is how on earth he acquired them. He wasn’t really a collector of other artists’ work.

“Landseer has been unfashionable for so long – apart from his wonderful landscape oil sketches – that I don’t suppose anybody really bothered with them. But there they were, tucked away.”

Gainsborough would later create imaginary landscapes using broccoli, moss and stones on his table. These drawings “do prove how much firmly rooted he was in the study of nature”, she said. “It underlines his very serious approach to landscape, which is quite novel in British art at this time. We are looking at quite an early phase in our landscape history.”

Hamilton said: “The landscape drawings that we know by him, particularly the later ones, are mainly inventions from his own imagination, drawn from a model he made – coal for rock, broccoli for trees, a little milk for a lake. These drawings do seem to have the breath of a breeze in them. He’s sitting on a stump in the landscape. He’s out in the field drawing. He hasn’t yet started being the artist of dreamy invention of landscape.”

The drawings – each about 41cm by 51cm (16 inches by 20 inches) in size – include banks of trees, lakes, donkeys and figures. One sheet has a portrait study of a young woman on the reverse, Stainton said, wondering whether this could be the artist’s future wife.

Razzall said that a second squared-up drawing in the album suggests that it was also planned for a painting.