The impact the Duke of Edinburgh's Award has had on thousands of people will be his everlasting legacy, Wales rugby captain Alun Wyn Jones has said.
The youth achievement award was established by Prince Philip in 1956.
Jones, a gold award holder and ambassador, said it taught him skills he had used in his rugby career.
"Whether it be life skills, independence, self-awareness - I've probably utilised those to some extent," he said.
"There's a lot of people I'm sure who'll have a lot of gratitude to be involved in the award," he added.
The programme aims to inspire and transform the lives of young people aged 14 to 24 through volunteering, physical activities and expeditions and operates in more than 140 countries.
It is based on the principles and philosophy of the UK's first Outward Bound centre, which was established in Aberdyfi, Gwynedd, in 1941.
The centre's pioneer was the duke's mentor German educationalist Kurt Hahn, who had also set up boarding school Gordonstoun, where the duke was educated.
Ian Gwilym is senior relationships manager at the DofE and also ran a DofE group at his local rugby club Ystradgynlais RFC in the Swansea Valley.
He said: "I've been fortunate to meet the Duke of Edinburgh on many occasions but more importantly thousands of young Welsh people have as well.
"The way he dealt with young people - with genuine interest, he had a certain grit. He related to young people… he had a genuine interest in finding out what they did for their DofE.
"There was always a little joke if young people had not done a foot expedition but done a canoe venture [instead] there was always a very humorous joke about canoeing being easier - 'sitting down and the river taking them through the miles of the countryside' - that does stick in my mind."
Mr Gwilym said he had witnessed young people being transformed after taking part in the programme: "It's a really powerful programme. The key ingredient is seeing young people grow in confidence.
"For certain individuals you will see them entering the DofE world as a shy person that struggles to converse, that has low self esteem... they have to become a team member and they have to communicate because when you're on an expedition in a strange mountain environment or a coastal path, if you shrink in that environment then it's not such an enjoyable experience."
Shuhani Shohid, from Newport, said the award instilled her with confidence and led her to a career as a primary school teacher.
"I was quite a shy individual who lacked a lot of confidence," she said.
"After attending the sessions for the bronze award and completing the expedition I was amazed how much I'd learnt about myself.
"I threw myself into so many activities I would never have done and being an ethnic minority in the community - a British Bangladeshi Muslim - doing these things is completely out of the norm."
She went on to complete her silver and gold awards and eventually became an ambassador.
"Once I became an ambassador and I saw the impact I can have on young people," she said.
"The Duke of Edinburgh has been a huge part of my journey in deciding my career."
Georgia Williams, from Flintshire, said she credited the award with getting her a university place.
"I didn't get my grades for university but in fact the experience I got on my DofE journey and the opportunities I gained from it actually allowed me to have my first choice university when I didn't have the grades," she said.
"I was such a shy girl but straight away I was chucked into not knowing anybody and in a completely different environment."
She said she had also been inspired to teach and was now a primary school teacher working in Luton
And she said she was thankful to the duke for creating the opportunity, which she said had "changed my life completely".
Ms Shohid agreed: "I'd like to say a huge, huge thank you to him for establishing the award… if it wasn't for the initial start it wouldn't have happened so definitely a huge thank you to him."
Mr Gwilym added: "I think his impact has been absolutely phenomenal.
"The programme has grown, the demand for the DofE today is stronger than its ever been and that's a fantastic legacy."
And Jones said the programme had a bright future: "The award itself will live on and his legacy will live long in the memories of everyone involved in the Duke of Edinburgh's Award."
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