Diana - Tenant 44-48

The switch back to Gilbert's narration at the end of chapter 44 was a bit abrupt. I'm curious as to his purpose in writing a 500 page letter to Halford. There must be some purpose, because Gilbert is laying everything out so methodically. Then at the end of chapter 48, we're suddenly pulled about fifteen years into the future. Who is Halford, and why is Gilbert writing to him?

If Helen were alive today, she'd probably be headed for counseling. She badgers people who care for her until she extracts promises that they will not try to see her (Hargrave, Markham 384). The irony is that she gave her future to a man who not only made her no promises, he made it quite clear before they married that he had no intention devoting himself to her. He implied he did not care about her feelings, and he has kept that implied promise, which has made her miserable. Although she is doing what is morally right, she is paying a terrible price to do so, because she didn't heed her aunt's advice.