A lot of the stuffy rules surrounding menswear are without merit, but there are a couple of really good reasons why you shouldn't break up your suit and wear the jacket and trousers separately:

• A jacket that looks like it belongs with a suit is probably going to look like an orphaned spare part when worn with other trousers.
• Trousers wear out faster than jackets; wearing the pants more will accelerate this.

That said, if your day's travels involve events with different degrees of formality, swapping out the top half of your suit is probably the easiest way to go from meeting to casual—you can always pull a polo or sweater out of your bag or trunk and change into it, whereas bringing along and hot-swapping into replacement trousers and shoes could (depending on situation) vary from inconvenient to grounds for arrest. And while a suit coat might not work without its matching pants, conversely there are no suit pants—even power-suit chalk stripes—for which you can't find a casual knit complement. Just pair patterns with a solid or vice versa.

Shown above: Wool/cashmere blend suit pants by Ernesto, merino sweater by... er... Express... shoes by Mezlan, belt by Calvin Klein.