 The mantle is a vestment or robe worn by members since the 15th century . Once made of wool , by the 16th century it was made of velvet . The mantle was originally purple , but varied during the 17th and 18th centuries between celestial blue , pale blue , royal blue , dark blue , violet , and ultramarine . Mantles are now dark blue and lined with white taffeta . The mantles of the Sovereign , the Prince of Wales , and Royal Knights and Ladies end in trains . The heraldic shield of St. George 's Cross encircled by the Garter is sewn onto the left shoulder of the mantle , but the Sovereign 's mantle instead has the star of the Order . Attached to the mantle over the right shoulder are a dark red velvet hood and surcoat , which have lost all function over time and appear to the modern observer simply as a splash of colour . 
