In Chapter 39 Lydia writes about the fun she's having in Brighton: "We dressed up Chamberlayne in woman's clothes on purpose to pass for a lady -- only think what fun! Not a soul knew of it, but Colonel and Mrs. Forster, and Kitty and me, except my aunt, for we were forced to borrow one of her gowns; and you cannot imagine how well he looked!"
Was this one of the officers? Wouldn't this have been scandalous behavior, even for Lydia? I find it to be quite shocking.