On Sunday, July 14, Middleton is expected to return to the tournament alongside Prince William for the men's singles finals.
The Duchess of Cambridge was first to arrive, and true to form, the dress of the day was one already.
The royal women had themselves a girls' day.
The smiles could be a stunt to appease Royal fans and observers that all is fine with the Royal household as rumours of an alleged feud between Kate Middleton and Meghan Markle have been going on for quite a while. Her sister Pippa dressed to impress too - sporting a pretty pink dress with floral detail from By Timo. While the duo appeared smiling and getting along, commentator Angela Mollard claimed their appearance was a "masterful" move the Duchess of Cambridge piloted.
Meghan is a close friend of Serena, who attended her wedding to Prince Harry a year ago.
But, despite their strong bond, the 37-year-old sportswoman won't be dishing out any parenting advice to the happy couple any time soon - even though she has 19-month-old daughter Alexis Olympia with husband Alexis Ohanian.
They weren't enough to hide the Duchess's nerves however, with the royal making several jittery asides to her sister-in-law.
Later on Halep met the Duchess of Cambridge - who is patron of the All England Lawn Tennis and Croquet Club - who congratulated the Romanian tennis player on her victory.
Kate is wearing a pale blue mid-length dress with nude heels, while William looks casual in a grey suit jacket with navy pants.
She replied: "You know, I didn't know there was negative media out there". This has a lot of Kate written all over, she's sort of seen to take the lead.