The silver coin, dated to 211 BC, was among a horde of more than 5,000 Iron Age and Roman coins found in a field near Hallaton eight years ago.

It is four years older than the coin thought to be the previous oldest surving example.

Archaeologists believe the horde was buried as a gift to the gods with other incredible finds, including a richly decorated Roman cavalry helmet, a unique silver bowl and the remains of over 300 pigs.

David Sprason, county council cabinet member for communities and wellbeing, said: "Leicestershire boasts the largest number of Iron Age coins ever professionally excavated in Britain in the Hallaton Treasure. To also have the oldest Roman coin ever found is something very special."

The coin, known as a denarius, depicts the goddess Roma wearing her characteristic helmet on the front.

The mythical twins, Castor and Pollux, sit astride galloping horses on the reverse.

The coins were first struck in Rome in 211 BC, making the Hallaton coin a very early version.

A soldier or unskilled worker living in the first century could expect to earn one denarius for a day's work.

That it was found among the Hallaton Treasure - unearthed from a site believed to have been a shrine built by the Iron Age Corieltavi tribe - has proved to be the biggest mystery for experts.

Archaeologists who researched the coin at the British Museum believe the fact that the coin is fairly worn suggests it spent 250 years in circulation on the continent, only later arriving in Britain in the purse of an invading Roman soldier post AD 43.

However, some archaeologists speculate that Roman Republican coins such as this were finding their way into Britain before the Roman conquest and are evidence of exchange through trade or diplomacy.

If this is the case, then the Hallaton coin is evidence of early Roman contact in the East Midlands, an area previously seen as something of a backwater during the Late Iron Age.