An ancient Roman coin showing a killer emperor has sold for more than half a million pounds.

It went under the hammer today for £552,000, more than five times the maximum estimate of £100,000.

It shows the head of Allectus, a finance minister who rose to the top by murdering his predecessor.

The gold coin, found near Dover, went this afternoon at an auction by Dix Noonan Webb, the Mayfair-based international coine, medal, banknote and jewellery specialist.

After fierce competition in the room, and on the internet and telephone, it was bought by a private collector over the phone.

The aureus is a relatively small gold coin weighing 4.31grams and slightly larger than a current penny.

It was found by a 30-year-old metal detectorist and his brother in March, next to a Roman road.

The detectorist, who wishes to remain anonymous now says: “I cannot believe it, we are ecstatic. We expected it to sell for a little over estimate, but not five times.

"We are sharing the money with the farmer, who is also thrilled.”

Christopher Webb, director and head of DNW’s coin department. said: “I am delighted with the phenomenal price achieved in today’s sale.

"This is the most expensive coin that we have ever sold.

"As well as being one of the world’s most expensive Roman coins, it is the most money ever paid for one of Allectus.

"It is now the most valuable Roman coin minted in Britain to have been sold at auction."

There are only 24 aurei of Allectus known worldwide.

Allectus was the finance minister for the emperor Carausius who controlled both Britain and Gaul, which is now France and neighbouring countries such as Belgium and Luxembourg.

Allectus seized power by assassinating Carausius in AD 293 but died in battle in 296.

The coins showing Allectus would only have been legal tender during his three years in power.

Deal has long been presumed to be the place were the invading Romans, led by Julius Caesar, first landed in Britain, in 55BC.

But in 2017 archaeologists argued that there was new evidence to show they had actually arrived at Pegwell Bay.

The Romans' name for Dover was Dubris and the most distinct reminder of their presence in the town is the Roman Painted House in New Street.

English Heritage also preserves a Roman fort in Sandwich.

Read more: All the latest news from Dover