When you think "men's suit," the image that almost certainly comes into your mind is of a lounge suit. This is the standard two or three-piece outfit of matching jacket and pants (and maybe vest), the hem of the jacket hanging a few inches below the waist, held together in front with two or three buttons (or one, if you're saucy). This is what every politician, business man, and job applicant wears. But for traditionalists, it's considered casual dress -- semi-formal at best. And that is simply not the state in which the prime minister of Britain attends the royal wedding.
The British have a reputation for taking their clothes seriously, which is causing something of a problem for a prime minister who has worked to tone down reminders of his tony background. David Cameron usually wears a lounge suit, even to weddings. He wore one to his own, in fact. But when his staff went ahead and said he would wear one to the wedding of Prince William and Kate Middleton, there was scandal. Alexander Chancellor wrote in The Guardian today: "[A] great patriotic occasion is a great patriotic occasion, and [the people] want it to be treated as such. As the press has pointed out, no party leader in memory has failed to wear tails at a royal wedding, not even a Labour party leader."
Chancellor points out that some of Cameron's younger days were spent in tails, making for the reputation he has worked hard to shake. "He did all he could to make people forget about his membership of the Bullingdon Club at Oxford, where he was embarrassingly photographed in white tie and tails amid a group of other equally arrogant-looking undergraduate members." On Wednesday, A Cameron spokesman said an aide had been misinformed and Cameron never intended to wear his work clothes.
Cameron wouldn't technically run afoul of the dress code if he wore a lounge suit. The invitation specifies "uniform, morning coat or lounge suit." (It is not appropriate to wear tails during the day.) But it would be the royal wedding equivalent of your disheveled brother wrapping a tie around his barely tucked-in denim shirt. It just wouldn't do.