Britain's coins have been tested for their metallic composition, weight and size in the country's oldest judicial process called the Trial of the Pyx, which carries the maximum punishment of imprisonment for the chancellor if the coinage is found to be of poor quality.

Officials from the Royal Mint on Tuesday brought close to 10,000 coins to King's Remembrancer, the oldest judicial office in the UK, to be counted and weighed in an official ceremony at Goldsmiths' Hall in London.

For the first time in seven decades, there will be coins with two monarchs' heads - Her Late Majesty and King Charles - which only happens when a monarch dies and a new reign begins.

Another unusual addition - a 15kg solid gold coin, the largest ever made - joins this year's collection.

The Trial of the Pyx, which has barely changed since the reign of Edward I, is not just ceremonial, but has a formal role as an external assessor of the work of the Royal Mint, the UK's official coinmaker. The coins represent one piece from every batch of each denomination minted.

The trial by jury, which takes place annually, dates back to the 12th century, when the ceremony was created to ensure that the coins produced by the Royal Mint were up to standard.

The jury must consist of at least six members of the Goldsmiths' Company, one of the 12 senior livery companies of the City of London, originally founded to support the gold-making trade.

The jury has powers to take action against the master of the mint, a role held by chancellor Jeremy Hunt. If the trial determines that the coinage is faulty, the chancellor can be fined, struck off or imprisoned.

The last master of the mint to be penalised by the jury was Isaac Newton in 1696. Another was sent to prison for six weeks in 1318.

The trial ensures that every coin produced by the Royal Mint meets a strict set of standards aimed at protecting consumers and that coins can, for example, be used in vending machines.

Throughout the year, coins are randomly selected and sealed in - the word pyx is derived from the Latin pyxis or small box - for the testing ceremony.

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British coins tested for quality in 700-year-old 'Trial of the Pyx'(https://www.ft.com/content/e70a612b-900d-4e34-a1bc-16d5c789497a)