The oldest coin dates to 152BC and is quite worn, showing bankers marks where checks were made on the purity of the silver, said Adrian Marsden

A hoard of 13 silver coins found in a field was probably lost in the wake of the Roman invasion of Britain in AD43, according to a historian.

The discovery was made by a metal detectorist in a field near Downham Market, Norfolk, in September and is the subject of a treasure inquest.

The denarii date from the late 2nd Century BC, in the last tumultuous decades of the Roman republic, to the first Roman emperors and could have been a purse loss.

"Of course, we've no way of knowing whose it was, but it could have been lost by one of the invaders," said coin expert Adrian Marsden.

Julius Caesar's Gallic Wars - in modern day France - are referenced with a coin struck in Spain after the Battle of Munda in 45BC

The Roman Republic lasted from 509 to 27BC and a series of unrest and civil wars in the 1st Century BC marked its transition to an empire.

"The oldest coin in the hoard dates back to 152BC and has worn smooth over the two centuries it was in use," said Dr Marsden, a numismatist from the Norfolk Historic Environment Service.

"This reveals they've got a stable economy, without changes to the denominations, so coins like this can remain in circulation for a long, long time."

One of denarii was struck by the Roman dictator Sulla (138 to 79BC), who won the first full-scale civil war in Roman history.

"Another was struck by Julius Caesar [about 100 to 44BC] a couple of years before he was assassinated, a second by Mark Antony [83 to 30BC] and a third by his rival and winner of that civil war, the first Roman emperor Augustus [63BC to AD14]," said Dr Marsden.

The story of how Augustus and Tiberius (above) became emperors was told in Robert Graves' novel I, Claudius

It was the latter's nephew, the emperor Claudius (10BC to 54AD), who ordered the invasion of Britain in AD43, eventually leading to a Romano-British province which lasted until 5th Century.

Dr Marsden described it as "one of the more interesting" hoards to cross his desk in the past year.

"It is earlier than most of the silver denarii hoards we see and it's got this drum roll of coins from the late republic through to the early empire," he said.

A coroner decides if a discovery is treasure and a museum usually gets first refusal over whether to add it to its collection.

In this case, the Lynn Museum in King's Lynn hopes to be able to acquire it.