To the untrained eye, they look like little more than blank, if rather old, sheets of paper.

In fact, Leonardo Da Vinci’s empty pages hold a secret few could imagine: more than a dozen studies of hands drawn in a metal substance turned to invisible ink over time.

The two pieces of paper, now known to be studies of the hands for the Adoration of the Magi, c1481, are to go on display to the public for the first time, at the Queen’s Gallery, Buckingham Palace, as part of the 500th anniversary of Leonardo’s death.