His large group portrait, "Banquet of the Amsterdam Civic Guard in Celebration of the Peace of Münster" (Rijksmuseum, Amsterdam), was painted in 1648, and exhibited to popular acclaim. It was this painting that sealed his fame for future generations, according to the Dutch artist biographer Arnold Houbraken. The painting was admired by Godfried Kneller and Joshua Reynolds. Van der Helst received a commission from the circle of the Stadtholder family, when he was asked in 1652 to paint the portrait of Mary, the widow of William II, Prince of Orange.