The first coinage featuring King Charles III will start to appear in circulation at Post Offices around the UK from Thursday, with millions of the new 50-pence coins bearing the new monarch's portrait given out as change to customers.

The coin with the 74-year-old monarch's image reflects a transition from the Elizabethan age of the late Queen Elizabeth II to the Carolean era of Charles, with the coin also commemorating the life and legacy of the Queen on its reverse.

"Today marks a new era for UK coinage, with the effigy of King Charles III appearing on 50ps in circulation. It's a fantastic opportunity for coin collectors to add to their collections, or start one for the first time," said Rebecca Morgan, Director of Collector Services at the Royal Mint.

"We anticipate a new generation of coin collectors emerging, with people keeping a close eye on their change to try and spot a new 50p that bears the portrait of our new King. The Royal Mint has been trusted to make coins bearing the Monarch's effigy for over 1,100 years and we are proud to continue this tradition into the reign of King Charles III," she said.

A total of 9.6 million 50 pences will enter circulation, with the rest entering in line with demand.

According to the Royal Mint, a commemorative version of the coin released in October saw record visitors to its website in the 24 hours following.

"It is a tremendous honour for the Post Office and for Postmasters that the first coinage featuring King Charles III is being released into circulation via our extensive branch network," said Nick Read, Chief Executive Office of the Post Office.

"December is our busiest time of the year so the coin will be entering our network in a phased manner. If you don't receive the new 50p in your change on your first visit to a Post Office you may well get it in your change in a subsequent visit, so keep a lookout for it," he said.

Starting this week, Post Office branches throughout the country will receive the first batch of 4.9 million 50 pence coins bearing the King's portrait, including the Aldwych branch which is close to Clarence House in London - the official residence of King Charles III.

The portrait has been created by renowned British sculptor Martin Jennings and has been personally approved by Charles.

In keeping with tradition, the King's portrait faces to the left, the opposite direction to his late mother Queen Elizabeth II.

The reverse, or tails side, of the 50 pence features a design that originally appeared on the 1953 Coronation Crown, struck to commemorate Queen Elizabeth II's coronation at Westminster Abbey and includes the four quarters of the Royal Arms depicted within a shield.

In between each shield is an emblem of the four nations that make up the United Kingdom - a rose for England, a thistle for Scotland, a shamrock for Northern Ireland, and a leek for Wales.

All UK coins bearing the portrait, or effigy, of Queen Elizabeth II will remain legal tender and in active circulation, as historically it has been commonplace for coins featuring the effigies of different monarchs to co-circulate.

This ensures a smooth transition, with minimal environmental impact and cost, the Royal Mint said.

There are approximately 27 billion coins currently circulating in the UK bearing the effigy of Queen Elizabeth II, to be replaced over time as they become damaged or worn out. Other denominations of coins will be manufactured carrying the King's effigy in line with demand.