Prince William added: "At the same time, I'm sorry that my father couldn't be here with us here today to say farewell, but I know he would talk of his fierce pride and admiration for you all, and of his own sadness to be moving on from an appointment he held so dear since 1975."
The new royal colonel described the Welsh Guards as having "always been a formidable group of soldiers" and that since being "raised for war in 1915", their battle honours underpin their "fighting spirit of today".
He also recalled his memories of his time in the Army that he had shared with the Welsh Guards Sniper Platoon Salisbury Plain as "some of my best" even though they "may not have been my easiest or driest days in the Army."
'A time I look back on fondly'
Prince William added: "Another key milestone in my life was also shared with the Welsh Guards, this time in the jungles of Belize as I received my A-Level results over the Bowman Radio.
"Many of you will know the feeling of being in the jungle; you're incredibly hot, continuously soaking wet and with nowhere to hide from potentially horrendous results, it could have been a really bad day!
"Ultimately though, it was the camaraderie, the togetherness, and, of course, the banter of the Welsh Guards that got me through that period, and it's a time I look back on fondly."
The event saw the Band of the Welsh Guards perform some Tom Jones classics to get the crowd warmed up, with the Guardsmen later lining up to receive the traditional St David's Day leeks from the Prince.
The Welsh national emblem has special significance for the soldiers, with legend saying the dark age King Cadwaladr ordered his men to attach leeks to their helmets to distinguish them from the enemy.
Welsh Guards Captain Michael Parry presented the Princess of Wales with her very own leek before miniature handmade leeks were given to the watching families on the parade ground.
Around 600 were on parade, not just the soldiers from the Welsh Guards, but regimental veterans and also soldiers from the 5th Royal Australian Regiment who are currently in the UK working as part of an international team helping to train the Ukrainian armed forces.