Teenager. Religious fanatic. Prostitute. The life and times of the worst Roman emperor you've never heard of.

On 8 June AD218 a fourteen-year-old Syrian boy led an army to battle in a Roman civil war. Rallying his retreating troops in person, against all expectations, he was victorious. Varius Avitus Bassianus, known to the modern world as Heliogabalus, was proclaimed emperor. The next four years were to be the strangest in the history of the empire.

Heliogabalus humiliated the prestigious Senators and threw extravagant dinner parties for his lower-class friends. He ousted Jupiter from his summit among the gods and replaced him with Elagabal. He married a Vestal Virgin twice. Rumours abounded that he was a prostitute, that he enjoyed sex with men, that he wanted his physicians to give him a vagina. His contemporaries were unanimous- Heliogabalus was the worst emperor ever. For Antonin Artaud, his life was 'anarchy in action'.

But we've forgotten all about him. How did a teenager from an obscure imperial outpost rise up to the very top? In the first biography of Heliogabalus in over half a century, Harry Sidebottom unveils the high drama of sex, religion, power and culture in Ancient Rome as we've never seen it before.