This was carried out by Mark Antony and Octavian - Caesar's adopted son - against Caesar's assassins, but the two eventually turned against each other, and the resulting war ended with Mark Antony's defeat in 31 BC. Octavian was consequently awarded the title of 'first citizen' by the senate - and this is thought to have been the first moment of properly imperial Rome.

Octavian became known as Augustus, and came to dominate the senate which was, at least in name, still the highest authority in Rome. The dynasty of Augustus led the Romans through a period of unprecedented peace and prosperity.

Octavian, or Augustus, was the first emperor of what became known as the Julio-Claudian dynasty. His rule was enormously successful in expanding the territory over which the empire ruled: he conquered parts of Egypt, Tunisia, Libya, and Algeria, as well as most of the northern Mediterranean. He also brought Roman control over the Iberian Peninsula, what is now Spain and Portugal, and made peace with the Parthian Empire in Iran to secure a stable border on the eastern frontier.

The Julio-Claudian dynasty includes Tiberius, Caligula, Claudius and Emperor Nero. Claudius began the conquest of Britain, which continued with great expansions under the reign of Vespasian and with Hadrian's famous wall across the Scottish border.

Nero's famously mercurial personality ruled unhappily in the year of the Great Fire of Rome, 64 AD, and his suicide led to a civil war known as the Year of the Four Emperors, 69 AD. This put an end to the Julio-Claudian dynasty.

The Flavian dynasty begins in 69 with Emperor Vespasian, who was the last of the Year of the Four Emperors. It was the emperor who built the famous Colosseum in Rome, which was completed and updated by his heirs Titus and Domitian (for this reason the structure is also known as the Flavian Amphitheatre).

Although plagued by a series of serious problems such as the eruption of Vesuvius in 79 which destroyed Pompeii and Herculaneum, and the fire and plague of Rome in 80 - Titus is considered a very able ruler. However, he died young, and his younger brother, Domitian, replaced him in 81.

Domitian was assassinated in 96, as he was known as an autocratic and severe emperor. He was replaced by an advisor, Nerva.

The dynasty that Nerva founded is known as the Nerva-Antoninus dynasty, and the five emperors that comprise it - Nerva himself, Trajan, Hadrian, Antoninus, and Marcus Aurelius - are known as the Five Good Emperors.

Trajan, the only Roman emperor not to have been born on the Italian peninsula, built the empire in its largest form. He conquered Dacia i.e. present-day Romania, Moldavia, parts of Bulgaria, Hungary, Ukraine, Slovakia, Serbia and Poland and Syria.

The Nerva-Antonine dynasty reigned between 96 and 192, and it is the reign of Commodus, the last of this dynasty, that is believed to mark the decline of the Roman Empire.

Like the British Empire and the Mongol Empire, the Roman Empire presided over a long period of peace – at least within the borders of its dominion. This became known as the Pax Romana, which allowed for a never-before-seen flourishing of trade.

In very practical terms, one of the main legacies of the Roman Empire was in engineering – in the construction of (notoriously very straight) roads and aqueducts. An aqueduct is used to move water, and the Romans built them and used them to bring water to cities, markets, and farms. The Segovia aqueduct, built during the reigns of Domitian, Nerva and Trajan, is a famous example.

As for the arts, Roman culture excelled in poetry, drama and sculpture… and anyone who studied Latin in school will know that we still study these achievements today, as they shaped the way we write, read and entertain ourselves, even today! Latin became the language of politics throughout Europe for nearly the next thousand years.

The subsequent Roman Empire - after its division - made Christianity the official religion, starting with the conversion of Constantine the Great. This led to the spread of religion, and Judeo-Christian culture in general, from east to west across the empire.

After the last of the good emperors, Marcus Aurelius, the reign of Commodus begins to mark the decline of the empire. In 192 he was assassinated, starting the Year of the Five Emperors. This introduced enormous political instability into the empire, culminating in the seizure of power by Septimius Severus in 193 (which set a precedent for the rest of the century).

After a series of barbarian invasions, and with plague and natural disasters ravaging the empire from within, Diocletian took control of the empire in 284 and ended the crisis. His response was to split the huge empire in two.

The eastern part would be ruled by Diocletian in Constantinople, or Istanbul, and would be known as the Byzantine Empire, along with the western one, whose center moved from Rome to Milan.

Eventually, both now-independent empires collapsed, although the eastern one lasted much longer as the Byzantine Empire.

It was Odoacer, the barbarian king of Italy, who caused the collapse of a Western empire severely weakened by incompetent leaders and invasions by Vandals, Ostrogoths and Visigoths. Odoacer, a Goth based in northern Italy, overthrew the last Western emperor, Romulus Augustulus, in 476.

The Eastern Roman Empire, better known as the Byzantine Empire, survived until its fall at the hands of the Ottoman Empire in 1453. Constantine the Great, the first Christian emperor, recovered the lands lost during the crisis of the third century, while Justinian (527-565) tried to reconquer the lands of the Western Empire.

Justinian's contributions to law, his sort of massive building projects, and his presiding over a period of greater prosperity have made him known to history as Justinian the Great... and also as the last Roman emperor

After this, Constantinople was finally conquered by Mehmed the Conqueror in 1453, the Ottoman emperor.