LONDON—Trafalgar Square's fourth plinth is reportedly being kept open for a posthumous statue of the Queen riding a horse. The Independent reports via "four well-placed sources" that the secretive plan has been in place for a while, but that even the Fourth Plinth Commissioning Group and the mayor of London were kept in the dark until recently.

Before he was elected, London Mayor Boris Johnson publicly supported a campaign to honor Battle of Britain hero Keith Park with a permanent statue on the plinth. But later, Johnson switched his position, writing, "The fourth plinth in Trafalgar Square would be a wonderful spot, but it appears complex planning issues would make it difficult to secure this location on an ongoing basis." According to the Independent, Johnson must have been informed of the plan for a statue of the Queen sometime after taking office.

The fourth plinth, sometimes referred to as the "empty plinth," held nothing between 1841 and 1999. Recently, contemporary artists have been chosen on a rotating basis to create temporary pieces for the column, with Antony Gormley and Yinka Shonibare chosen to create the next two works.

The Queen has been painted by a number of artists, but there are no statues of her in the capital, and only one in the U.K. — in Windsor Great Park. One source suggested to the Independent that the Trafalgar Square work be erected now, since the plan has become public knowledge. "She certainly deserves it," the source said.