When summer is at its zenith and the sallow foliage develops a bluish tinge, a giant butterfly – beautiful, bold and brazen – flies powerfully over the tree canopy. Females of this species, wary yet determined, haunt the sallow thickets, depositing their eggs, while the males establish treetop territories and descend to the woodland floor in search of indelicacies to feed upon. Mysterious, elusive and enthralling in equal measure, this is the butterfly that Victorian collectors yearned for above all others: His Imperial Majesty, the Purple Emperor.

A wondrous enigma, the Purple Emperor is our most elusive and least-known butterfly – we glimpse it only through fissures in its treetop world, yet this giant insect has fascinated us for centuries and has even inspired its own 'Emperoring' language. Matthew Oates became captivated by the Purple Emperor following his first sighting as a boy. He has studied it assiduously ever since, devoting his life to trying to unravel the Emperor's secrets.

His Imperial Majesty takes us on a journey, beginning with a dalliance into the bizarre history of our engagement with the butterfly, with daring doings and gross eccentricities from the Victorian and Edwardian eras. Subsequent chapters explore all aspects of this remarkable butterfly's life cycle, including behaviour, habitat preferences, life history and conservation, all relayed in Matthew's unique, informative and witty style. Not so long ago, our knowledge of the Emperor was largely based on a blend of mythology and assumption. This book dispels the fabrications and reveals all about the Purple Emperor – the king of British butterflies.