Clare Balding heads out across Windsor Great Park in the company of writer and prolific walker, Bill Bryson. He explains how he developed a passion for exploring both Britain and parts of America on foot. They discuss how ones notion of distance changes dramatically when you walk.

'A mile becomes a long way, two miles literally considerable, ten miles whopping, fifty miles at the very limits of conception. The world, you realize, is enormous in a way that only you and a small community of fellow hikers know. Planetary scale is your little secret.'

Bill takes Clare on one of his very favourite walks around Windsor Park, a place he has enjoyed walking with his family.

Producer Lucy Lunt.