Why do we never talk about Heliogabalus? For those who enjoy stories of depraved Roman emperors, he knocks the sandals off Caligula and Nero. The nicknames he acquired after a reign of just four years (AD 218–22) bear witness to his reputation. These include Gynnis (‘womanish-man’), Koryphos (either ‘virgin-rapist’ or ‘catamite’) and Tiberinus, because his dismembered remains were thrown into the Tiber.

Heliogabalus was not chosen for his skills in government. He came to the throne at the age of fourteen, propelled to power by the women of the ruling Severan dynasty after the assassination of the Emperor Caracalla. Heliogabalus was a relation of Caracalla, but the royal women put about a rumour that he was in fact Caracalla’s illegitimate son in order to shore up his claim to the emperorship against a rival from outside the family. This deceit helped him to win over some of the legions, who led him to victory in a brief civil war.

The Severan women hoped to exert their own political power by controlling this teenage emperor. However, they did not reckon with his remarkable capacity to upset every constituency of Roman opinion. Take, for example, his choice of palace officials. Not only did he give a number of posts to those from outside the senatorial aristocracy; he also, according to some accounts, used penis size as the most important criterion in the selection process. For instance, the freeman Zoticus, the son of a cook from Smyrna, secured the post of imperial chamberlain thanks to his large endowment. Not for long, however. A similarly advantaged Carian charioteer, Hierocles, caught the emperor’s eye and elbowed out Zoticus by drugging him with an anaphrodisiac which left him unable to perform to the emperor’s satisfaction. So much did Hierocles please Heliogabalus that they went through a form of same-sex marriage. Heliogabalus wanted not only to make Hierocles deputy emperor, but also (after being caught with other men) to be beaten by Hierocles as a sign of his passive role as a ‘wife’.

Heliogabalus’s addiction to eccentric luxury upset Rome as much as his feminine passivity. Dinner invitations from him were best avoided. Guests might be served wax copies or paintings of food while the emperor enjoyed the real thing. Or there might be a banquet in which every course consisted of just one ingredient – pheasant, for example, or ostrich – or just one colour. Real food might be mixed with inedible objects: lentils with onyx, or beans with amber. Tame beasts might be released between courses, to the terror of the guests, or guests might be invited to a twenty-two course dinner where they were required to have sex between each course. At one dinner, he is said to have drowned the guests with flower petals released from secret awnings, a story that inspired Sir Lawrence Alma-Tadema’s painting The Roses of Heliogabalus.

Worse than all of this, however, was his attitude to religion. Heliogabalus was descended from the royal family of the city of Emesa in Syria and was particularly dedicated to that place’s god, Elagabal, of whom he was a priest. The god’s cultic object was a black stone, which Heliogabalus set up in a grand temple in Rome. He then scandalised Rome by trying to make its traditional gods, including Jupiter, subordinate to this eastern newcomer. Perhaps in a similar spirit, Heliogabalus broke an extreme taboo by marrying a Vestal Virgin. It was one of four marriages he entered during his four-year reign.

These tales of flower petal asphyxiation and macrophallocracy are entertaining, but are they true? The source material is famously unreliable. One of the most raucous accounts, the late fourth-century Augustan History, is for the greater part a work of creative fiction. In recent years the academic fashion has been to treat all of the written sources on Heliogabalus with extreme scepticism, and to doubt whether very much at all can be known about him. The author of this new biography, Harry Sidebottom, who is both a historical novelist and an Oxford classics don, pushes against this trend. His account, which combines down-to-earth scholarly rigour with highly entertaining storytelling, critiques a number of received academic ideas. For example, he denies the notion that successive Roman emperors created an ‘official narrative’ hostile to Heliogabalus that was then parroted by contemporary historical writers. He also argues that just because the reports of the emperor’s actions echo those relating to a predecessor and thus appear to be topoi, or literary commonplaces, does not necessarily mean that they are untrue. This being so, he analyses the sources in a more generous, but still forensic, manner. One might disagree with some specific judgements, but his overall approach shows considerable sense.

Sidebottom’s account of Heliogabalus’s life offers much more than just eyebrow-raising tales of imperial debauches. Sidebottom uses Heliogabalus’s career to investigate a whole host of historical questions. These include the role and capacity of the emperor, how Roman women could exert political power, the nature of religious extremism in the period and whether racism existed in ancient Rome. On all of these subjects, Sidebottom is refreshingly independent-minded and argues his case rigorously and with clarity. This biography should ensure that we pay more attention to Heliogabalus, and not just on account of the wildness of his dinner parties.