But charcoal is an exception. The only other is probably black, which is restricted to evening wear (though the French have a curious fondness for the black suit).
Charcoal brings out little in brown shoes: something about the darkness and simplicity of the colour demands black calf. There is little subtlety or movement to a dark grey suit. Even a mid-grey worsted with little surface detail has variation in tone as it moves which complements a brown shoe, such is its usual patina.
And of course charcoal is just very dark, likely the darkest and most devoid of colour in a man’s wardrobe. If one’s shoes look best when they are darker than the trousers above them, black is the only option.
This suitability of charcoal and black is particularly true for a flannel suit, as in the illustration above (Ralph Lauren, A/W 2010). The only exception here might be a dark brown suede shoe, perhaps a slip-on, the matching of textures enough to distract from the disparity in colour.
Few men, particularly in London, wear brown shoes well. One recommendation I would have for them is to always wear black shoes with charcoal.