'Caligula', more properly Gaius (Gaius Julius Caesar Germanicus), was the third Roman emperor, in succession to Tiberius. He has gone down in history, perhaps unfairly, as Rome's most tyrannical emperor, but since we lack Tacitus' account of his short reign, it is impossible to know the truth behind the wilder stories.

Gaius was the son of the popular Germanicus and the great-grandson of Augustus - with the blood of Augustus from both sides of his family. From age two to four he lived on the Rhine with his father's legions, and the soldiers gave him the affectionate nickname 'Caligula', or 'Bootikins'.

After the death of his brother in 33 AD he was, with Gemellus (grandson of Tiberius), next in succession, and lived with Tiberius on Capreae. When Tiberius died in 37 AD, the Praetorian Prefect Macro ensured that Gaius, not Gemellus, became emperor. It was also rumoured that Gaius and the Praetorian Prefect Macro had hastened the death of Tiberius by smothering him with a pillow. Gemellus and Macro were both put to death at the beginning of the new reign.

The 24-year-old emperor was initially hugely popular - he was the son of Germanicus, had the blood of Augustus in his veins, and was a welcome change from the dour, absent Tiberius.

Departing from his predecessor's frugality, he provided lavish games for the Romans to enjoy, and abolished the sales tax. But seven months into his reign he fell ill, and he emerged from this as a megalomaniac - he may have lost his sanity, though this is doubtful.

He went out of his way to humiliate the senate (Suetonius says that he intended to make his horse consul), and encouraged treason trials for his own financial benefit. He also insisted on being treated as a god (in contrast to the wiser policy of Augustus). Excavations in the Roman forum in the summer of 2003 confirmed that he incorporated the ancient Temple of Castor and Pollux within his palace - a sacrilege reversed by his successor Claudius I.

Gaius had three sisters, with whom he was alleged to have committed incest, and they were given unprecedented public honours, being included in the soldiers' oath of allegiance. But Drusilla died in 38 AD, and the next year Agrippina and Livilla were exiled for involvement in a conspiracy.

In 39-40 AD, Gaius campaigned in Germany, as his father had done. More mysterious was his planned expedition against Britain in 40 AD. He got no further than the Channel, where he ordered the troops to gather seashells, a command which, despite many attempts, has not yet been satisfactorily explained.

His actions suggest that he needed military glory such as Augustus and Tiberius had enjoyed, but did not want the bother (or the expense) of a war. His triumph on his return in 40 AD was thought to have featured bogus Germans (slaves in disguise). He also particularly offended the Jews, intending to place a statue of himself in the Temple at Jerusalem.

In 41 AD, the Praetorian Guard assassinated Gaius, together with his wife Caesonia and his daughter. He was 29. Only the common people, who benefited from his extravagant spending, lamented his death.