Camilla in Royal Family painting

The paintings will be on display at the Mall Galleries, London

The first group portrait of the Royal Family to include the Duchess of Cornwall is to go on public display.

The painting, by Sergei Pavlenko, set outside the Old College at Sandhurst, commemorates Prince Harry's graduation from the military academy.

The artwork also depicts all the members of the senior monarchy.

It will be on display this week at the Royal Society of Portrait Painters' annual exhibition in London, along with three other sketches by the artist.

Mr Pavlenko, who previously painted an image of the Queen that was used for a postage stamp, said the painting was an "interesting challenge".

Princes William and Harry posed separately for the artist

"If you want to paint a good portrait it doesn't matter if the person is old or young, a man, woman or child, from that point of view they were like all of us.

"But because they are royal public figures it's an interesting challenge and brings more interest to my work because it becomes historical."

Live sittings

Mr Pavlenko began working on the group portrait, which was commissioned by Sandhurst, several months before Harry's graduation.

Some of the subjects, including Princes William and Harry, posed separately for the artist.

He then assembled the Queen and other royals after Prince Harry's graduation ceremony from the academy last April.

"At that stage I was looking at what poses they would take, how they would stand, their relation to each other in terms of height and light," said Mr Pavlenko.

"I wasn't concerned about the facial expression. Those would be done during the live sittings."

Sketches by Mr Pavlenko will also be on display

Senior royals had a preview of the nearly-finished painting when it was hung at Sandhurst's Old College in Camberley, Surrey, during Prince Harry's graduation.

Mr Pavlenko said: "I asked Princes William and Harry if they liked it and they said 'yes' and when the Royal Family saw it at Sandhurst they all liked it," the artist said.

The portrait will be on display at the Mall Galleries, London, from Thursday to 13 May before returning to Sandhurst.

Three sketches in oils, including one of Camilla and another of William and Harry, will also be on show.

A spokesman for the Royal Society of Portrait Painters said: "The work is part of the tradition of portraits as works of historical record."