The day after the christening of Prince William and Kate Middleton's third child, Prince Louis, the proud parents, accompanied by Prince Harry and his new wife Meghan Markle, attended the 100th birthday celebrations of the Royal Air Force.
The Duchess of Cambridge is clad in an icy blue Alexander McQueen dress with three-quarter length sleeves and her signature neckline, which she's paired with a matching hat by Sean Barrett and nude heels.
Her choice of Givenchy is an unsurprising one since she has become an ardent champion of the French fashion house under Claire Waight Keller's creative direction in recent months, and famously wore her custom design on her wedding day.
Watched by the Queen and senior members of the royal family from the balcony of Buckingham Palace, the spectacle drew awe and applause from the crowd below.
Jeff Spicer via Getty Images Queen Elizabeth II at the RAF centenary celebration.
Earlier the royals attended a service at Westminster Abbey along with dignitaries including Theresa May, Jeremy Corbyn and the defence secretary, Gavin Williamson.
In Ireland they will spend their time visiting organisations which are "central to Irish life", including the home of Gaelic football and the country's most famous university.
Meghan the Duchess of Sussex was all smiles through her second appearance on the balcony of Buckingham Palace. Meetings with The President of Ireland, Michael Higgins, and with The Taoiseach, Leo Varadkar, are both planned.
Lincolnshire's RAF Red Arrows and the Battle of Britain Memorial Flight Lancaster will fly over Buckingham Palace for the flypast at 1pm.
The RAF, which is the first-ever independent air force, split from the British Army and Royal Navy in April 1918.
A century later, the RAF is engaged in 13 missions across 26 countries and is heavily committed on operations both at home and overseas, according to Buckingham Palace.