In 1866 Planché was promoted to the office of Somerset Herald. For most of that year he was engaged in editing "Clarke's Introduction to Heraldry". During his heraldic duties, Planché came across a hitherto-neglected manuscript in the collections of the College of Arms; this became known as "Planché's Roll", since he was the first to draw attention to it. He also left another heraldic legacy; Ursula Cull, the wife of future Garter King of Arms Sir George Bellew, was a descendant of Planché's daughter Matilda.