When impoverished aristocrat Lady Charlotte Bertie married wealthy Welsh ironmaster John Guest of Dowlais in 1833, her relatives looked on with dismay. Yet despite their vast difference of background and age, over their nineteen-year long marriage, husband and wife enjoyed great happiness and much adventure. There would be ten children and while John built up an immense commercial empire, Charlotte championed Welsh culture.

Crucially, she taught herself John's business from the inside. Over the years, she made the keenest observation of iron production, the fluctuations of the trade and the engineering innovations that touched upon its developments. When John died in 1852, she was therefore uniquely well-placed to succeed him as head of the works - a remarkable position for a Victorian woman. Not only did she endeavour to introduce reforms, but also - rather to her dismay - had to weather a potentially destructive strike.

But success came at a price. With her star to all sight in the ascendant, Lady Charlotte suddenly chose to abandon all, leave Wales and marry her sons' tutor. This book traces the ardent, creative years of her first marriage, explores her determination - widowed - to preserve John's legacy, and observes her growing devotion to the scholarly Charles Schreiber.