A gold signet ring that belonged to a former prime minister has been sold at auction for £9,500 after being found in a field.

It was discovered in a pasture for sheep near Aylesbury, Buckinghamshire, by 85-year-old metal detectorist Tom Clark.

Later it was identified as belonging to George Grenville, who was UK prime minister between 1763 and 1765.

The ring sold during an auction at Noonans Mayfair to a buyer in the USA.

Mr Clarke was pleased with the result yet admitted: “I didn’t watch the sale as I was out metal-detecting.

“I would like to put the money in my bank account, but I am sure that my wife will have ideas of how to spend it!”

The 18th Century prime minister was dismissed by King George III after the acts he introduced caused protests in what were then the American colonies.

His ring was passed to his second son, also a member of Parliament, named George, according to Nigel Mills, artefact and coin expert at Noonans.

He served as Lord Lieutenant of Ireland, was given the title of Marquess of Buckingham and lived close to where the ring was found.

Half of the proceeds from the sale will be given to the land owner.