What's the Fourth Wall in a History Book?

Onam says he's spent a lot of time thinking about what makes a good history book. He wants to make it entertaining and authoritative, while still having authority. The writing style is incredibly good: lightness of touch with the writing but moving parts as well. And that's what his new book does - challenges you to think of things in a different way. Onam also reveals how Goon Show creator Antpomber Brentall helped him get through an event at Jimmy Grafton's pub where they were born.