Painted by Steven van der Meulen, the rendering is the earliest known, full-length portrait of the monarch, the BBC said.

The work had been expected to fetch between $1.4 million and $2 million at auction, Sotheby's said.

"Like her father, Henry VIII, she was incredibly conscious of how important her image was," said Emmeline Hallmark of Sotheby's. "This painting is so pretty and decorative, and the symbolism alludes to the fact that she is in the ripeness of her life."

The portrait hung for 50 years on the wall of a private meeting room at Aylesbury Crown Court in Buckinghamshire, the BBC said.