The first episode charts the early days of the romance of Marengo and Copenhagen, the horses of Napoleon and the Duke of Wellington. It is the beginning of the Peninsular Campaign and as their love blossoms, the shadow of impending combat looms over the two heroes.

Deep in the British Library tucked into the slipcover of a book on the history of Blenheim Palace a packet of extraordinary letters has been discovered.

"Dear Marengo brackets Napoleon's horse close brackets, I've never written a letter like this before..." thus begins the first passionate letter from Copenhagen, the Duke of Wellington's horse, to his hero Marengo in this epistolary equine love story.

The first episode charts the early days of their romance and the beginning of the Peninsular Campaign. As their love blossoms, the shadow of impending combat looms over the two heroes.