] I think they are napoleonic. They look it, but it would have been a bit insensitive, seeing as the wars were being fought at the time (hence the shortage of men and the horrible social faux pas that Mr Darcy makes by not dancing).

Do you mean french? Not particularly, no. The British Navy wore them, with great effect on the general populace ;) It may be that the fad originated in '01, after Trafalgar, but the particular type of hat had been around for yonks by 1813. It's a bicorne, and it's related to the tricorne of the early 18th c.

The most plausible explanation is that the Court at St James was oldfashioned before Prinney, and that men's formal fashions were at a standstill because of this. The Chapeau Bras is a late 18th c hat.

I'm sure Louisa P's got some great plates with men carrying chapeaux bras. Jessamyn has two great prints on her site, linked below.