A coin found on a Devon farm by a metal detectorist has been sold for £648,000 at auction. 

Experts have managed to link the coin to a single, probable owner: a 13th century nobleman who paid the king to get out of serving him. 

Michael Leigh-Mallory found the coin in September 2024. 

An example of Henry's gold pennies, of which only eight exist.

The environmentalist was working on the farm when he took a chance with his metal detector. 

The coin he found is a Henry III Gold Penny, one of the rarest coins in British numismatic history, and last month it was auctioned by Spink in London. 

The coin was issued in 1257 as Henry III attempted to restore his kingdom to gold coinage. The experiment was not a success and the coins were only minted for around a year. 

This coin, academics say, was almost certainly owned by John de Hyden, who was Lord of Hemyock Manor, close to where Mr Leigh-Mallory made his find. 

De Hyden is on record as having paid 120 grams of gold to the king to avoid jury service and a public office. He subsequently served on Henry’s campaign in Wales in 1257. The king used his new coins to pay for the expedition, distributing 37,000 of them. 

Dinefwr Castle in Wales, one of targets of Henry's 1257 campaign, funded with his new gold coins. 

Only eight are known to survive today, with just two of those outside institutional collections. 

Collectors from around the world attended Spink’s January sale by phone and online to try to secure the rarity, which was sold after spirited bidding. 

The Treasure Act regulates finds like this one in order to allow some precious finds to be preserved as national heritage. 

They are rewarded with a portion of any sale price. 

Mr Leigh-Mallory says he will spend his money on funding the education of his two children.

He said: “How it has survived three-quarters of a millennium relatively unscathed is truly miraculous. Like every hobbyist who continues to dream, my wish that day came true, and I just happened to be the very fortunate one.”

The coin is now the most valuable single coin ever found in Britain and the most valuable single British medieval coin. 

A wonderful achievement from a moment of sharp-eyed searching.