First portrait of William and Harry unveiled at National Portrait Gallery

They may be dressed in military uniform but the pose is casual.

Artist Nicky Philipps has captured the "brotherly relationship" of Princes William and Harry in the first commissioned portrait of them together.

The work was unveiled at the National Portrait Gallery today.

The princes sat for Philipps between August and December 2008 in the Household Cavalry Number One Dress Ceremonial uniform, known as "the Blues", which they wore for the Queen's birthday parade that year.

At the time William was a lieutenant in the Household Cavalry, although he is now training to be a search and rescue pilot with the RAF, while Harry was - and remains - a lieutenant in the same regiment.

Philipps, 45, who lives and works in South Kensington, said the princes were "very good company".

"Although I was commissioned to paint them in their official context, I hope I have also captured some of the brotherly banter that characterised the sittings," she said.

It was, she added, a "behind-the-scenes glance at the human element of royal responsibility" and emphasised their "brotherly relationship".

The National Portrait Gallery's director, Sandy Nairne, said the portrait "captures them formally dressed, but informally posed."

The brothers are pictured in the library of Clarence House, the home of the late Queen Mother, which has been their official residence since 2002. William is wearing a riband, the blue garter sash, and a Jubilee medal which was given to him at the Queen's Jubilee, and his Garter Star medal, which he received when he became a Knight of the Garter in June 2008. Harry is also wearing a Jubilee medal and his campaign medal from Afghanistan.

The painting of the princes, now aged 27 and 25, can be seen free in the Contemporary Galleries alongside other royal portraits from the last century.