According to Boots and Bonnets,
Breeches were replaced by pantaloons, which were tighter fitting and extended to mid calf or below. These were bias cut to achieve a much closer fit. They were worn with highly polished tall boots. Between 1807-25 trousers, originally worn by working men, appeared as an alternative. They were skin tight to the knees and below the knee they were looser and anchored in place by straps under the instep, a device possibly introduced by Brummell to ensure the trousers’ unwrinkled perfection could be maintained. Breeches, pantaloons and trousers in this period fastened with a side buttoned rectangular panel to produce a flat front to the garment and preserve the closeness of fit.This is all very well. But I have to wonder whether all these skin tight garments were not sometimes rather...revealing? When Lady Barbara Childe walked into a room having damped her petticoats so they would cling to her body, was it not obvious that the men present were affected by the sight? Codpieces were no longer in fashion, and as far as I can tell, male underwear mostly consisted of cotton drawers. Does anyone know how this worked? Did young Regency girls just have to determinedly look at men's faces? I'm told that the "modesty girdle" took a while later to come into existence - what exactly was happening in between?