The first official painting of the Duchess of Cambridge was today highly praised by Britain's most prolific royal portrait artist.

Richard Stone, who has painted most members of the Royal Family during the past three decades, said the work by Paul Emsley had captured Kate's evident warmth and approachability.

He said of the portrait: "I liked it, very much so. So often with official portraits they can be rather stiff and starchy, but this has a lovely informality about it, and a warmth to it.

"I haven't met the Duchess of Cambridge, but by all accounts and obviously from the photographs and on television, she comes across as an extremely warm and approachable person, and that seems to be exactly what he has captured.

"It was jolly brave of him to paint it well over life size, because that's extremely difficult. It's very challenging to do something larger than life, and he seems to have pulled it off very well."

Mr Stone's first royal commission was to paint the Queen Mother, and he went on to do so six times.