Since Kate is on maternity leave, she wasn't expected to attend the event, though Westminster Abbey confirmed she would be there when they released the order of service on their Twitter account in the early hours of Tuesday morning. Appearances like this are rare for Kate, as she just welcomed Prince Louis April 23 and won't be doing public events regularly until the fall following her maternity leave.
The outlet reported that Kate felt the celebration was important to be at if she was feeling up to it.
The 36-year-old pinned the priceless piece on the fold of her pale blue Alexander McQueen coat dress.
Come Saturday, all eyes will be on her sister, Kate, who will join Meghan in cheering on Serena Williams.
She attended her brother-in-law's wedding in May, Trooping the Colour in June, and now the RAF centenary commemorations. To release, Middleton chose a stylish dress from your favorite British brand Alexander McQueen.
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The film has been in development for a while but picked up momentum in January when Jac Schaeffer was tapped to pen the script. Shortland, who has been regarded as the frontrunner to direct the film, is best known for directing Berlin Syndrome and Lore .
Meghan channelled the Duchess of Cambridge with nearly matching shoes - a nude pointed-toe pump and held a little clutch in her hand. Middleton, who is expecting her first child, wore a white broderie anglaise dress by the same label for her first Wimbledon appearance on July 5.
The dress appeared to be the exact same style to the lemon one she wore to Prince Harry and Meghan Markle's May wedding, which is also identical to the cream one the Duchess wore for Princess Charlotte's Christening in 2015.
Led by the Queen, the royals were attending a service to mark the centenary of the Royal Air Force. Prince William and Prince Harry were decked out in their military finest.
Kate Middleton wore a light brown hat designed by Jane Taylor to Prince Louis's christening.