When the first official royal portrait of the Princess of Wales was unveiled 10 years ago, Kate Middleton was typically gracious, describing Scottish artist Paul Emsley’s efforts as “brilliant, absolutely stunning”.

Critics however were less kind, calling it “appalling”, “rotten” and “an absolute disaster”.

Now, although it is the only portrait of the future Queen of Britain in the National Portrait Gallery, the painting has been “unfixed” and moved into storage.

According to a Daily Mail exclusive, the gallery informs that anyone interested can see it “after an appointment in our archive”, but without explaining the reasons why the portrait was removed from the collection.

Princess Catherine is the Royal Patron of the gallery in Trafalgar Square and the first official joint portrait with Prince William was recently unveiled.

“It is inconceivable that Her Royal Highness’ painting would be removed from public view without being consulted,” a source said. “That would be very rude. She is our precious protector.”

However, as the mystery rages and the painting remains in storage, so do rumors that the future queen may be deeply glad that the work is no longer on public view.