Waiting for God S03 E04 Harvey's Fiancee

"A Comedy About Growing Old Disgracefully"

Baines meets a girl-friend, Lucy Maitland, at the hunt ball. His mother is coming to visit before going to stay with his sister so Jane poses as Lucy Maitland to put Mother off Harvey's new fiancee whilst Tom and Diana ham it up mercilessly pretending to be Baines' parents talking to Lucy. The result is that Lucy does not stay around and Jane has got her Baines back all to herself.