The annual exhibition of the Royal Society of Portrait Painters had obtained the painting from Prince Charles.
The canvas, which usually graces the walls of Clarence House, depicts a smiling Camilla, glowing in smooth skin.
Artist Susan Crawford, whose expertise lies in painting horses and human portraits, painted the informal image last year.
"Having known the Duchess and her family for many years I wanted to bring out the informal side of her character, her adaptability and above all her sense of humour," the Daily Express quoted Crawford as saying.
"She inherited many of these qualities from her father, Bruce Shand, of whom I was very fond," she added.
RSPP spokesman Richard Fitzwilliams further said: "There's a charm in this portrait, also a humanity and a sense of humour. It's a striking image." (ANI)