King Charles vented his frustration at a leaky pen on Tuesday during a signing ceremony in Northern Ireland, the second time in recent days he has shown visible irritation during such proceedings.

Charles, visiting Northern Ireland as part of a tour of the United Kingdom to lead mourning for his mother Queen Elizabeth, was greeted by cheering crowds and welcoming speeches, before delivering his own pledge to the region.

Shortly after, when signing a visitors' book in front of cameras at Hillsborough Castle near Belfast, Charles reacted in frustration when a pen he was using leaked on his hand.

"Oh God I hate this [pen]!" Charles said, standing up and handing the pen to his wife and Queen Consort, Camilla.

"Oh look, it's going everywhere," Camilla said as Charles wiped his fingers.

"I can't bear this bloody thing... every stinking time," Charles said as he walked away.

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