But, why was Brad invited and why did he attend?
Brad Pitt and Jennifer Aniston.
On the same weekend as the Grammys and the BAFTAs, Aniston organized a star-studded party to celebrate her 50th birthday, and the guest-list was truly astounding.
"Happy Birthday to this fierce Woman", Theroux wrote in the caption. "She debated back and forth with friends if she should invite him", an insider told People magazine in another report. However, Pitt was spotted arriving at the party wearing a flat cap, making it hard to make out if it was him.
No Hollywood party is complete without a photo booth to capture memories of the big night, and judging by social media Jen's pals made great use of the facility at the Sunset hotel.
Party guests included Pitt's ex Gwyneth Paltrow, plus Aniston's ex John Mayer and his ex Katy Perry, who was joined by beau Orlando Bloom.
Aniston reportedly didn't give Pitt any special treatment, however.
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'Since they split, her friends believe that their plan to move forward in life without each other was the best decision for them both. "They're not necessarily close, but more friendly".
Aniston and Theroux tied the knot in 2015, before they announced their split in 2018 after two and a half years in marriage.
The two separated at the end of 2017. "In an effort to reduce any further speculation, we have chose to announce our separation", they said in a joint statement. "This decision was mutual and lovingly made at the end of a year ago".
As a source told Entertainment Tonight, "They are friends and have supported each other through some tough times".
Pitt and Aniston were married from 2000 to 2005.
It was previously claimed Jennifer and Brad had got back in contact following his 2016 split from Angelina Jolie. They were married just a few years later with a bond that seemed unbreakable - that is, until Mr. and Mrs. Smith happened.