Other couples that come close to the ideal difference include Hollywood actor Brad Pitt, 50, and Angelina Jolie, 38, and Daniel Craig, 46, and Rachel Weisz, 44 - both with gaps of four inches.
"The long and short of it is that size does matter to a lot of couples. And the height of romance appears to be when the man is five inches taller than the woman, just like William and Kate," said a spokesman of Lovehoney.
