Who is Mr. Arbuthnot from The Enchanted April and what is their importance?

Mr. Arbuthnot is the only character with an actual second identity. This second identity fulfills his physical needs, and his attraction to Lady Caroline can be seen as an attempt to meet those needs in ways his wife refuses to do. It is obvious, however, that Mr. and Mrs. Arbuthnot love and desire each other in spite of the various barriers between them.