My friend Ben said he heard I wrote a book called The Frog theory. He told me his mother studied frogs in the Russian mountains, and her hosts produced fresh, cool milk with the tea. As she stared at the milk, wondering how they kept it cold, with no electricity or fridges – a live frog popped up and ribbited, before disappearing once more beneath the surface.

   ‘There’s a frog in the milk!’ She exclaimed.

   ‘Yes yes’ said her host, ‘it’s to keep it fresh.’

Hmmm. Was I being teased again, I wondered?

   ‘I’m serious.’ Said Ben. ‘Look it up!’ I did. And it was true. Before modern refrigeration, some people in Russia and Finland preserved milk by placing a live frog in it.