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Kate visited the battalion's home base in Aldershot, Hampshire, to continue the Royal tradition which dates back more than 100 years.
Kate Middleton wore a green Emilia Wickstead dress coat bought especially for the occasion, with a brown Lock & Co hat, brown suede shoes and a gold shamrock brooch, which has been handed down through the Royal family and was once worn by the Queen Mother.
Kate was greeted by Commanding Officer Major General William Cubbitt before making her way to the parade ground where 450 soldiers, in full ceremonial uniform of scarlet tunics and bearskins, were waiting for her.
The military band played the first few bars of God Save The Queen as Kate readied herself to present the shamrocks to the 40 Officers and Warrant Officers. Those officers then issued shamrocks along the ranks as the band played Irish folk song Carrickfergus.
Kate also presented a sprig of shamrock to six-year-old Irish Wolfhound Conmeal, the regimental mascot.
Drummer Oliver Vaughey, 22, who has been a dog handler for two-and-a-half years, said: "He was presented with a shamrock by the Duchess of Cambridge. People saw him shake his collar, probably as a thank you. He has been our mascot for four years and always marches in front of the regiment."