On a whistlestop visit to Tata Steel the Prince commemorated the rebuilding of blast furnace number four - a major £185 million project.
He was then shown a video about the lightweight super-strength steel which could transform safety for British soldiers.
As Charles was taken around the marquee, children from Eastern Primary School performed a series of festive songs.
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Outbreaks of light rain or drizzle expected around the coast and hills.
Mike and Cynthia from Ystradgynlais flew out to the German city for a weekend away.
Fine and dry at first but becoming largely cloudy with outbreaks of rain or drizzle.