King Charles has been seen airing his frustration during a ceremony for the second time in four days while in Northern Ireland.

The new monarch was shown signing a visitor’s book in front of cameras at Hillsborough Castle, near Belfast. He reacted after the pen he was using leaked on him.

“Oh god I hate this (pen)!” Charles said, standing up and handing the pen to his wife, Camilla, Queen Consort.

“Oh look, it’s going everywhere,” Camilla said as her husband wiped his fingers.

“I can’t bear this bloody thing … every stinking time,” Charles said as he walked away.

When completing the documents on Tuesday he also used the wrong date, before checking with an aide who told him it was 13 September not 12 September.

The King had earlier been greeted by crowds in Belfast, and delivered his own pledge to the region.

The visit to Northern Ireland is part of a tour of the United Kingdom in the days since Queen Elizabeth died.

The new monarch has had a busy schedule since his mother’s death at Balmoral in Scotland on Thursday. He returned to London on Friday, then after engagements including his accession ceremony at St James’s Palace and addressing MPs and Lords at Westminster Hall, flew back to Edinburgh on Monday where he walked behind the Queen’s coffin and later stood over it at a vigil with his siblings.

At the accession council on Saturday, an irritated Charles had signalled for aides to move a pen holder and pens that had got in his way as he signed documents.

There was some sympathy for the monarch as social media users reflected on his grief at the loss of his mother and his hectic schedule since her death.

The Times’ history correspondent Jack Blackburn tweeted: “I think it’s possible to read too much into a bit of grouchiness from someone who has been travelling non-stop since his mother died last Thursday.”

Former political editor of the Jewish Chronicle, Marcus Dysch said: “Watching the news last night I thought aside from the grief, King Charles must be absolutely exhausted. He is in his 70s and flying round the country almost non-stop. Clear it is getting to him. Hope in due course he gets the time he needs to deal with this traumatic period.”

After his visit to Northern Ireland he returned to Buckingham Palace on Tuesday evening where he will receive his mother’s coffin, which has been flown from Edinburgh accompanied by Princess Anne.