Diego Sarmiento de Acuña was born in Gondomar, in Galicia and served as Spanish Ambassador from Philip III and Philip IV to James I in England between 1613-18 and 1620-22. He exercised great influence on James I and brought about the negotiations for a marriage between the Prince of Wales and the Spanish Infanta. This picture was probably painted in London in 1617, when both artist and sitter were in England.

Sarmiento was created Count Gondomar in 1617 and was also a Knight of the Order of Calatrava, one of the earliest Spanish military orders originally established in the 12th century. The sitter is depicted wearing the badge of the Order, a Greek cross with a fleur-de-lis at each end, on a heavy chain around his neck.