Monday's Order of the Garter Day was full of pomp and pageantry, and this year's ceremony was extra special with the attendance of King Felipe and King Willem-Alexander, who were invested as Supernumerary Knights of the Garters by the Queen, in the presence of their respective wives, Queen Letizia and Queen Maxima.
Royal fans followed the spectacle from around the world and many were quick to notice that the Duchess of Cambridge did not curtsy to Queen Letizia when they saw each other at the Galilee Porch.
Kate and the Duchess of Cornwall talking to Queen Letizia
The clip in question, which was shared online, shows the Duchess of Cambridge and Queen Maxima arriving at the Porch by car after the Duchess of Cornwall and Queen Letizia, who had arrived minutes earlier.
As Kate and Maxima exit their royal car, they can be seen walking swiftly past Camilla and Letizia, and positioning themselves behind them, with no curtsy in sight. The Countess of Wessex and Sir Timothy Laurence's car can be seen pulling in quickly after.
Kate curtsying to the Queen
Many were quick to question why Prince William's wife had not curtsied to King Felipe of Spain's spouse, but HELLO! understands the ladies had met minutes earlier at the Castle, before entering their cars and making their way to the Galilee Porch to watch the procession go by.
Protocol dictates that a curtsy only has to be done once, when first meeting the monarch, so even though it wasn't captured on camera, Kate would have curtsied to Queen Letizia earlier in the day.
The Duchess of Cambridge, 37, and Queen Letizia, 46, showed off on Monday how well they get on, chatting away whilst waiting for their husbands to arrive. It's not the first time the royal wives have spent time together. Back in 2011, Letizia attended the royal wedding of Prince William and Kate and six years later, they were reunited again at the Spanish state banquet. The ladies are expected to reunite once again at Ascot on Tuesday.