This is a variant of the portrait by Lely of the sitter in armour, of circa 1675, at Chirk Castle. The sitter's grandfather Sir Thomas Myddelton (1586-1666), was at first a prominent parliamentarian, but in 1659 joined Sir George Booth's rising in favour of the recall of King Charles II. This resulted in the siege, and destruction of one side, of Chirk Castle by General Lambert. Sir Thomas's son, Thomas, was created a baronet in 1660. The 1st baronet had two sons: Thomas (the sitter in the present portrait), and Richard.
Thomas, who succeeded as 2nd baronet on his father's death in 1663, was Member of Parliament for Denbigh. He was painted by a variety of different artists including Wright, Wissing and Riley. On his death in 1684, the baronetcy passed to his brother Richard who was also Member of Parliament for Denbigh, 1685-1716.
We are grateful to Sir Oliver Millar for informing us of the identity of the sitter.