Horses were a driving force behind medieval England's agricultural and economic expansion, although little has been written about the trade in these animals or how they were supplied. In the first book of its kind, Jordan Claridge addresses this gap, revealing that although lords and their estates relied heavily on horse power, they largely failed to produce agricultural horses themselves. Instead, it was England's peasants who bred the workhorses that fuelled the medieval economy. Peasants exploited opportunities in seigniorial society and identified conditions suited to horse breeding, coming to dominate the production and trade of working horses. Through meticulous analysis of manorial records, Claridge uncovers how peasant production not only sustained medieval English agriculture but also contributed to England's commercialization and long-term economic development. In so doing, he highlights the unexpected role of ordinary people in shaping economic transformation.