The pregnant Duchess sported a light blue Matthew Williamson coat dress and tall black boots for the occasion and accessorised her look with a pair of glittering green amethyst earrings by Kiki McDonough. Although small, the Duchess' baby bump was visible as she waved to royal fans who lined the street outside the refinery.
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It was a musical welcome for Prince George's parents as two young ladies playing the harp and the flute honoured their arrival.
The refinery, which is celebrating 50 years since it was officially opened by the Queen Mother, said William and Kate's visit was a "huge honour".
After touring the refinery the couple were treated to a performance by the Young Actors Studio, who work in partnership with the refinery through The Royal Welsh College of Music and Drama.
Following their engagement in Pembroke, the parents-to-be travelled to Cardiff's Millennium Stadium to watch a rugby match between Wales and Australia.
For the past week the Duke and Duchess of Cambridge have been off-duty and spending time Queen's Balmoral estate in Scotland.