Kate Middleton is decked out in green for St Patrick's Day as she and William put on affectionate display

Kate Middleton and Prince William on St Patrick's Day

Catherine, Duchess of Cambridge and Prince William, Duke Of Cambridge attend the annual Irish Guards St Patrick's Day Parade at Cavalry Barracks on March 17, 2018 in Hounslow, England. (Photo by Andrew Parsons - WPA Pool/Getty Images)

Catherine, Duchess of Cambridge attaches a sprig of shamrock to the regimental mascot, the Irish wolfhound 'Donal' during the annual Irish Guards St Patrick's Day Parade at Cavalry Barracks on March 17, 2018 in Hounslow, England. (Photo by Chris Jackson/Getty Images)

Catherine, Duchess of Cambridge and Prince William, Duke Of Cambridge stand on the dias during the annual Irish Guards St Patrick's Day Parade at Cavalry Barracks on March 17, 2018 in Hounslow, England. (Photo by Andrew Parsons - WPA Pool/Getty Images)

Catherine, Duchess of Cambridge presents the 1st Battalion Irish Guardsmen with shamrocks during the annual Irish Guards St Patrick's Day Parade at Cavalry Barracks on March 17, 2018 in Hounslow, England. (Photo by Chris Jackson/Getty Images)

The Duchess of Cambridge presents shamrock to officers and guardsmen of 1st Battalion the Irish Guards as she and the Duke of Cambridge attend the regiment's St Patrick's Day parade at Cavalry Barracks in Hounslow

The Duchess of Cambridge attends the regiment's St Patrick's Day parade at Cavalry Barracks in Hounslow, to present shamrock to officers and guardsmen of 1st Battalion the Irish Guards

The Duchess of Cambridge and the Duke of Cambridge attend the Irish Guards St Patrick's Day parade at Cavalry Barracks in Hounslow

The Duchess of Cambridge attends the regiment's St Patrick's Day parade at Cavalry Barracks in Hounslow, to present shamrock to officers and guardsmen of 1st Battalion the Irish Guards

Catherine, Duchess of Cambridge attends the annual Irish Guards St Patrick's Day Parade at Cavalry Barracks on March 17, 2018 in Hounslow, England. (Photo by Chris Jackson/Getty Images)

Caitlin McBride Twitter Email

March 17 2018 1:02 PM

Kate Middleton and Prince William were uncharacteristically affectionate today as they attended a parade of the Irish Guards for St Patrick's Day in London.

Britain's Duchess of Cambridge is expecting the couple's third child, due next month, and made her annual appearance alongside her husband in Hounslow in West London, as William is the colonel of the Irish Guards.

Kate opted for an altered maternity piece by one of her favourite designers Catherine Walker, a deep green coat, wrapping up for the cold conditions with black fur cuffs and a headpiece by Gina Foster, which she first wore to the St Patrick's Day celebrations in 2014. She wore a generous xxx of shamrock below her shamrock brooch, which she has traditionally worn at the celebrations since marrying into the British royal family in 2011.

As part of her duties, the expectant princess presented shamrocks to officers. 350 soldiers, as well as their proud families, were present for today's festivities. But perhaps it was Irish wolfhound Domhnall, whom the royals have met before, who stole the show - at least Kate's heart.

Kate and William were uncharacteristically affectionate today, perhaps taking a leaf out of Prince Harry and fiancée Meghan Markle's more relaxed playbook.

Last year, William sipped on a pint of Guinness as a nod to the tradition of the day.