Heir to the throne Charles, who was invested as by the Queen on July 1 1969, cut a cake in celebration of his historic day after sipping a cup of tea from a china cup bearing the emblem of the Welsh red dragon.
He visited a Prince’s Trust call centre in Nantgarw near the Welsh capital Cardiff on Monday, meeting workers at the charity’s helpline and young people who have benefited from its advice.
The prince stood with his hands behind his back and listened as Philip Jones, director of the Prince’s Trust Cymru, paid tribute to his commitment to Wales and spoke about the investiture in 1969.
“It was an important day then and it’s an important day for us because since then your dedication, support and love of the Welsh people has been extraordinary – not least through the work of your trust, the Prince’s Trust here in Wales,” Mr Jones said.
“During that time many thousands of young people have been helped into employment, to learn the life skills to get on in life, or indeed to set up their own business.”
The prince began a week in Wales – during which he will carry out more than a dozen engagements throughout the country – with a service at Llandaff Cathedral in Cardiff as Colonel-in-Chief of the 1st The Queen’s Dragoon Guards (The Welsh Cavalry), which is celebrating its 60th anniversary.
He also encountered horses in Ty’n-y-Coed Forest when he met horse loggers in his role as patron of The British Horse Loggers.
The organisation promotes using horses as sustainable “base machines” in the extraction of timber, and Charles was told about their impact on the Llantrisant woodland.
At the Prince’s Trust helpline run at Connect Assist, Charles was presented with a celebratory cake by Sian Hartstill, senior head of operations at the trust in Wales, who told him it marked his visit and his “momentous occasion”.
The prince took the large knife, wrapping his fist around it and plunging it into the middle of square sponge cake that was covered in white icing and decorated with a Prince’s Trust emblem.
“The excitement is to get it out, it suddenly comes popping up in your face,” the prince joked as he lifted a piece on to the top of cake.
Charles, who is the longest-serving heir to the throne and Prince of Wales in history, was also presented with an anniversary present – a set of cuff links and a tie pin by Llandeilo-based jeweller Mari Thomas.
Ms Thomas, who was helped by the trust to set up her business 21 years ago, handed over the gifts, which were made of oxidised silver and etched with words in Welsh from the poem Cofio – which translates as Remembrance – by Waldo Williams.
The prince described the presents as “fantastic” and quizzed Ms Thomas on how her business was going.
Charles did a small double fist pump in celebration after Ms Thomas told him she was now employing 10 people, with the jeweller adding: “Thanks to your support, so thank you very much.”
A crowd of more than 100 helpline workers gathered outside to say farewell to the prince, with a smiling Charles quipping “good God, they’ve brought you all out” before chatting to those in the front row.
He set up the Prince’s Trust in 1976, using his Navy severance pay, to help young people overcome challenging circumstances, get into employment or launch their own businesses.
The trust has helped nearly one million young people to date.
At Connect Assist, Charles met Bethan George, who got a job on the helpline after completing a Prince’s Trust programme.
The 22-year old from Caerphilly said: “I showed him a live chat where young people message us online. He said that was a really helpful way to come through.”
Charles was made the Prince of Wales by the Queen when he was just nine, on July 26 1958.
He was formally invested with the title by his mother amid great pomp and ceremony at Caernarfon Castle in north Wales at the age of 20.
The prince’s investiture ceremony was televised and watched by an audience of 19 million people in the UK and millions more worldwide.
A fresh-faced Charles knelt before the Queen to receive the insignia of office and pledge allegiance.
Fifty years on, the Second Severn Crossing was renamed the Prince of Wales Bridge last year to honour Charles’s 70th birthday, 60 years since he took on the title in 1958.
The structure links England to Wales by extending the M4 across the Severn estuary – but the decision caused controversy.
Plaid Cymru’s then-leader Leanne Wood tweeted: “Is this a late April fool joke?”
An online petition opposing the change attracted thousands of signatures.
Charles’s anniversary coincides with the birthday of his late ex-wife Diana, Princess of Wales, who would have been 58.