This episode is brought to you by Network Rail.

It's easy to disappear into your own bubble when you're out and about,

whether you're lost in your thoughts or lost in nature.

The last thing on your mind is the danger of trains at level crossings.

Beware the bubble, stay aware, take care and help us keep you safe at level crossings.

It is 346 BC in the ancient kingdom of Macedonia,

on the northern fringes of modern-day Greece.

The sun blazes down on a crowd assembled on an open air horse market

on the plains outside the capital Pella.

Pomegranate trees stand unmoving in the still air, heavy with their crimson fruit.

A boy whose name is Alexander watches as nobles and others dressed in cotton tunics

and leather sandals walk around examining the fine beasts.

But one animal in particular catches the boy's eye,

a wild, giant black stallion which is refusing to be mounted.

The magnificent horse snorts and shakes its head.

A royal attendant highly experienced in taming horses,

ducks out of the way as it kicks its powerful back legs.

He slowly circles before trying to grab the reins and mount it again.

But the horse rears up, a wild look in its eyes,

throwing the attendant onto the hard ground with a loud thumb.

Its hooves clatter back down, and it starts to run, scattering the nobles and servants.

The Macedonians are proud horsemen, and none more so than Alexander's father,

...