The work, which was gifted to the trust in 2010, shows the artist wearing a black velvet cap with two ostrich feathers, a decorative metal band worn round the neck and a short, decorated velvet cape.
It was signed and dated 1635, but its authenticity was long questioned by some art historians who considered parts of the work to be inferior.
However, the piece was confirmed as genuine by the Hamilton Kerr Institute in 2014 and was valued at £30m.
John Chu, a Senior National Curator at the trust, said the artist appeared both “swaggering” and “tentative” in the picture, with a “mysterious” shadow across his face.
The work will begin its tour at Kingston Lacy near Wimborne and will visit Dunham Massey and Upton House in 2026 before returning to its home at Buckland Abbey in Devon.
