In 1842 one of the most important collections of the eighteenth century was sold at auction, that assembled by writer and collector Horace Walpole at Strawberry Hill, the eccentric Gothic Revival castle he built just outside London between 1751 and 1797. As Head Curator at Strawberry Hill, my main task in recent years has been to trace down the whereabouts of Walpole’s lost treasures. One of the objects that were most admired by Walpole—the portrait of Bianca Capello, Grand Duchess of Tuscany (1548-1587)—is of great relevance to this symposium. The invention of the word “serendipity” is in fact linked to this portrait, which to date has not been traced. In this presentation, I will discuss and analyse the events that led Walpole to the invention of the concept of serendipity.