Who is Lady Joan Bailey from Possession: A Romance and what is their importance?

Lady Joan Bailey is an elderly woman in a wheelchair. She has a large, moon-shaped face dotted with brown age spots, big pale brown eyes, and smooth, gray hair pulled back at the sides. Lady Joan lives in Seal Court with her husband, Sir George. She is a romantic and becomes an ally to Roland and Maud. She is often a calming influence on her husband.