Sam Kean

The price of diamonds can vary greatly depending on size, cut, color, and other factors, including whether they have a history. But because of the rarity of blue boron diamonds, they often fetch more money than gems of similar quality.

All my grandchildren bake. On a Saturday, Annabel's boys, Louis and Toby, always bake. Louis makes a chocolate cake, Toby makes banana or lemon drizzle. They're 12 and 10, and they can do it totally on their own. My son's twin girls, Abby and Grace, are 14; they make birthday cakes and like to do it on their own with Mum out of the way.