A question about Mr. Bennet

In Chapter 43 Mr/Bennet thinks sending Lydia away is the best course of action.

"Lydia will never be easy until she has exposed herself in some public place or other, and we can never expect her to do it with so little expense or inconvenience to her family as under the present circumstances..."

It isn't until around chapter 46 that Mr. Bennet learns what a mistake this was.