William, who is Colonel of the Irish Guards, and Kate were visiting 1st Battalion at their base in Hounslow, west London.

The parade began with the Last Post, before a minute's silence was observed by the royals, the Irish Guards and their families who stood in memory of the 50 victims.

From Galway to New York, events are being held across countries with parades and parties to mark Ireland's National Day, when revellers traditionally dress in green.

The sun shone as Kate handed out baskets of shamrock.

Close behind was her husband in his Irish Guards Frock Coat in the rank of colonel.

After Kate presented the shamrock to officers and warrant officers, three cheers were raised to the royal duo before a march past where William took the salute.

About 350 soldiers marched on the Parade Square at Cavalry Barracks on Sunday morning.

Their families proudly watched on wrapped up warm with blankets to protect from the cold March wind.

Leading the procession was Irish wolfhound and mascot Domnhall, whom Kate patted and stroked several times while presenting him with a shamrock.

Drummer David Murray, his regimental handler, said the St Patrick's Day parade was "number one" in his calendar and like a "second birthday".

The mascot, wearing a red coat, was presented with his first shamrock in 2013 and led the regimental band and parade.

Australian Associated Press