Not so very long ago, everyone knew how to ride a horse. Today, the biggest link most of us still have with horses is the races. Martin's company's horse, Buffalo Stampede, is running at Fontwell racecourse in Sussex for the first time in a year since a leg injury. The horse tires and comes in last, but Martin is just glad to see it cross the finishing line without injury.
The everyday traffic of horses may have vanished from London's streets. But the British monarchy still uses horses - and plenty of them - to keep tradition alive.
Martin's final journey is to one of the remotest parts of Central Asia to meet some of the world's greatest horse people. He experiences life among the nomadic Kazakh tribes people, virtually unchanged since they first harnessed the power of the horse 6,000 years ago. Nowhere on earth is there a culture still so utterly reliant on the horse.