The Duke has attended the bi-annual two-day event from a young age but has but has never before taken the salute – which is when a senior officer or VIP formally acknowledges a salute given by troops. He beamed from the platform, enthralled by the ceremony.
Sitting on the saluting dais, the 31-year-old Prince enjoyed the magnificent display of pomp a pageantry, which featured 300 musicians, drummers and pipers from the UK, Canada and France.
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A 6,500-strong crowd at the 500-year-old ceremony were treated to a display of military horsemanship, precision drill, gunfire and fireworks based on the theme of cooperation during the First and Second World Wars.
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For the traditional occasion William sported the black uniform of the Irish Guards, the regiment of which he became Royal Colonel in February 2011, two months before he married Kate Middleton.
Addressing the performers and spectators Prince William spoke of his pride at seeing the age-old event in his military capacity.
"As Colonel of the Irish Guards I am delighted to support the Household Division Beating Retreat," he said. "Year after year this wonderful event showcases the skill and professionalism of our military musicians whilst reinforcing the traditions and heritage for which we as a nation are justifiably proud and envied the world over.
"As we begin our centenary commemorations of the First World War, I am particularly pleased to welcome our friends from Canada and France to Horse Guards Parade.
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"Our linkages with both nations remain as strong as ever and continue to be reinforced through current military operations in Afghanistan and elsewhere."