Complex sentence: The hammerbeam roof is concealed by a decorated plasterwork ceiling dating from the 17th century, with a broad coving; the decoration to both ceiling and coving includes painted coats of arms, which were probably added in the 19th century.
Split into simpler sentences: The hammerbeam roof is concealed by a decorated plasterwork ceiling, probably dating from the 17th century. It has broad coving decorated with painted coats of arms, probably added in the 19th century.