Although it's not essential, a simple black, navy or dark knitted tie is a great addition if you don't have one already. It should be about 2 1/2" wide.

"Even though [knitted ties] are quite fashionable at present, they've been around for decades," says Wilcox. "They add a casual, relaxed flair to a shirt at the weekend -- or even during the week with a suit. It's like 'sort-of-wearing-a-tie.' "

But keep it classic and get it from an old-school vendor, Wilcox advises.