A wide range of commemorative coins are being struck - from the rare kilo coin to the £5 silver which will be more readily available.
The two arrived late after their helicopter was forced to make an emergency landing minutes after taking off from central London.
Tributes have been paid to Princess Lilian, both in Scandinavia and in Swansea where she was born, after her death at the age of 97.
The Duchess of Cambridge has made her first public appearance since the birth of her baby as she joined Prince William, starting a charity endurance marathon on Anglesey.
Baby George didn't make the trip, but as his father's time at RAF Valley, and in Wales comes to an end, hundreds of people did turn out to see the couple before they leave Wales for good. Ian Lang reports.
Prince William and the Duchess of Cambridge have arrived in Anglesey to start an ultra marathon, it marks the first time Kate has been on a public engagement since the birth of Prince George.
The Duke and Duchess of Cambridge looked relaxed and happy as they shared a joke with runners in Anglesey.
Wearing a tweed jacket and slim black trousers the Kate laughed as she met some of the runners and their families and volunteers before the start of the ultra marathon.
The Duchess of Cambridge's decision to join her husband at the launch of an ultra-marathon today was a surprise and her attendance was only revealed this morning.
The royal couple have lived on Anglesey for years and have always spoken of their love of the island.
William said a public goodbye a fortnight ago as he confirmed his young family would be leaving their Welsh home and moving "elsewhere" when his posting comes to an end this month, having completed his three-year tour as an RAF search and rescue helicopter pilot based at RAF Valley on Anglesey.
The Duchess of Cambridge will join Prince William when he starts the Anglesey ultra marathon today.
But the royal couple will appear without Prince George.
The Duke of Cambridge is making one of his final public engagements on Anglesey as the new father's time on the island comes to an end.
William will be joined by Kate as he starts the gruelling, three-day annual "ultra" marathon run around the coast of the island, known as the Ring O' Fire.
The Duke and Duchess will meet some of the runners and their families and volunteers before the start - but the couple will not be bringing the royal baby.
The annual event is a 135-mile foot race around the rugged coast of Anglesey, staged over three days and including 13,695 feet of ascent.
The last time the Duchess was seen in public was the day after the birth of Prince George.
The Duke of Cambridge will start the Ring O'Fire Anglesey Coastal Ultra Marathon on Anglesey later. The Ultra Marathon is an annual 135 mile coastal marathon circumnavigating the Isle of Anglesey. The foot race is staged over three days and follows the Anglesey Coastal Path around the island.
Prince William will meet a number of runners and their families and a selection of volunteers involved in the administration of the race before officially starting the Ultra Marathon.
The 135 mile distance and 13,695 feet of vertical ascent makes the Ring O' Fire one of the most extreme ultra marathons in the United Kingdom.
Prince William is to leave his home and his job as an RAF Pilot on Anglesey at the end of next month. He was speaking at the Anglesey show on his first official engagement in Wales since returning here from paternity leave. He show goers by demonstrating his Welsh.
Prince William told the crowds at the Anglesey Show today that he and Kate will miss the area terribly when his posting comes to an end next month.
The duke was on his second official public appearance since the birth of Prince George.
He watched gundog and falconry displays, before meeting local young farmers in North Wales.
In a speech he said he was sorry Kate couldn't be there and joked that his son was "very good looking."
William in on a three-year tour as an RAF search and rescue helicopter pilot at RAF Valley in Anglesey which finishes at the end of September.