There is a little point of detail that is often overlooked, in relation to trouser breaks (the way they fall on the shoe). Formal morning and evening trousers should have a whisper of a break, a horizontal crease, at the front and should decline over the top of the back of the shoe. However, otherwise, trousers should fall just on the top of the shoe, without a break. I am not entirely sure of the origin of this differentiation but it might have something to do with Edward VII's introduction of turn-ups or cuffs on country trousers; rolling them up to save them from the mud. Therefore, maybe, informal trousers became that little bit shorter than formal ones, thanks to Edward The Peacemaker. The pictures demonstrate the difference.