The painting shows an old, weary man slumped in contemplation in his armchair and has spent more time in the National Gallery's storeroom than on display because it is attributed to a follower of Rembrandt rather than the artist himself.
But the gallery is being urged to rethink. The academic widely acknowledged as the world's leading expert on Rembrandt is about to drop an art historical bombshell by arguing it was not only painted by the 17th century Dutch master himself, but it is also a pivotal work for the artist.
"It is of wonderful quality and is revolutionary in a sense," Ernst van de Wetering told the Guardian. "It is a very important painting."