Gemma is so frustrated she throws the book across the room. John picks it up and dusts off the cover.

"That's a first edition," he says. "And it has been out of print for thirty years."

"I've noticed a direct correlation between the age and rarity of your books and the usefulness of them," she says.

"Oh, good," John says with a sigh of relief. "You're catching on. I was worried you were still missing your collection of sparkly new age crap from Waterstone's."

Gemma throws another book, this time at John. He just laughs.