Prince William and Kate delight guests at Northern Ireland garden party

The Duke and Duchess of Cambridge were the royal guests of honour on Tuesday afternoon (June 14) as they stepped out in Northern Ireland for the Secretary of State for Northern Ireland's garden party. Some 2,500 guests joined the royal couple at the party, hosted on the gorgeous grounds of Hillsborough Castle.

Prince William and Kate arrived shortly after 4 pm to cheers from the crowds of fellow guests. They were led onto the steps of the grand residence by Secretary of State Theresa Villiers before going to mingle with guests in the gardens.

TAP TO VIEW FULL GALLERYWilliam and Kate were in good spirits as they arrived at the garden party

Kate opted to wear a recycled Day Birger coat for the occasion, completing her look with a hat by Lock & Co and the Irish Guards brooch. Meanwhile William wore a navy suit and blue tie.

The Secretary of State for Northern Ireland has hosted the garden party annually since 1984. Guests are invited in recognition of their work with charities or within their communities, and a royal guest of honour attends each year.

Kate looked stylish in a Day Birger coat

In 2015 the honour fell to the Earl and Countess of Wessex, while the Queen and Duke of Edinburgh attended in 2014 during their visit to Northern Ireland.

William and Kate's appearance at the party comes just hours after they visited the US Embassy in London to sign a book of condolences for the victims of the nightclub shooting in Orlando. The royals looked sombre as they were greeted by the US Ambassador in London, Matthew Barzun, before adding their comments.

After signing, the Duke and Duchess spoke with reps from the US embassy's LGBT network GLIFAA. As a mark of respect, Kate wore a knee-length black-and-white dress teamed with a cropped black blazer.

Their message read: "With our deepest condolences and with our thoughts and prayers to all those affected. William, Catherine."

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