For most British weddings, a top hat and tails for men and daytime formal with a hat for women is about as fancy as it gets, but if the groom has served in the military it adds a whole new layer of pomp. William wore his Irish Guards Mounted Officer's uniform for his wedding, and Harry will follow in his spurs-clanking footsteps – although exactly which uniform Harry chooses to marry in won't be revealed until the day.