The Prince and Princess of Wales have celebrated St Patrick's Day alongside the Irish Guards, with Kate hailing their "boundless, irreverent, glorious sense of humour".
William, who said he was "incredibly sad" to be marking the end of his time as Colonel of the regiment, was joined by Kate who officially became Colonel on Friday.
The couple were attending the St Patrick's Day Parade at Mons Barracks in Aldershot, Hampshire.
Princess Kate, fittingly dressed in an emerald green outfit with matching heels, presented sprigs of shamrock to the officers and guardsmen as well as to the Irish wolfhound regimental mascot Turlough Mor, also known as Seamus.
As rain lashed down on the parade ground, the band of the Irish Guards played tunes including music from Bill Whelan's Riverdance.
In a speech, William said: "Whilst I am extremely happy to be here celebrating St Patrick's Day with you once again, I'm incredibly sad to be giving this speech, as it really does mean my time as your colonel has come to an end.
"It has been one of the great honours of my life to hold that title; I’m proud of everything it stands for – just as I'm immensely proud of every single one of you."
He added: "It's also no secret that while at Sandhurst I had a potential officer's visit to the Irish Guards, an experience that placed this battalion firmly at the top of my personal wish list.
"Operational reasons alone prevented me serving my frontline years with The Micks.
"I have, however, relished every opportunity to visit you – I just wish the opportunities had been far more frequent.
"From exercises and range days here in the UK, to training overseas – such as Kenya in 2018 – I have such vivid memories of witnessing what you do so brilliantly in the field."
Speaking about his wife, the Prince said: "I may be stepping aside, but in Colonel Catherine, you have a committed, focused and already incredibly loyal 11th Colonel.
"As you serve together over the years ahead, know that I will continue to watch you, with huge pride in having been one of you."
Taking to the microphone after William, Kate said: "I really couldn't be prouder to stand in front of you here today.
"It really is a true honour to be your Colonel. I am here to listen to you, to support you, and to champion you in all you do – this is a responsibility I do not take lightly.
"Last week, I took the opportunity to visit some of you on Salisbury Plain, to see your inspiring work for myself.
"The day was bitterly cold, and while displaying your skills to yet another visitor was probably the last thing any of you wanted to do, all I saw was enthusiasm, pride and incredible dedication."
'Boundless, irreverent, glorious sense of humour'
Princess Kate added: "I was hugely impressed with your insistence that nothing is as bad as it seems, and – most of all – your boundless, irreverent, glorious sense of humour.
"That's what makes you who you are and what makes the Irish Guards unique.
"I look forward to spending more time with you and your families, seeing your commitment to duty and service in all you do.
"Before I close, however, I want to thank Colonel William. He has always talked about his fierce pride for this regiment. I know he will continue to support us all in the work we do," she added.
The parade concluded with a royal salute and march past, where Kate took the salute as the new colonel.
After the parade, the princess was presented with flowers and the couple met the Irish Guards Association, which is made up of past members of the Irish Guards.
The visit ended indoors in a packed hall with William taking a pint of Guinness and Kate nursing a half pint.
The couple mingled with Irish Guards, chatting about Army life and Saturday's big rugby clash between Ireland and England.