updated 08/14/2012 AT 2:00 PM ET
•originally published 08/15/2012 AT 8:00 AM ET
On Aug. 10, Theroux’s birthday, the pair of 15 months sat side by side at a corner table at Blue Hill restaurant in Manhattan, enjoying a quiet dinner and looking “like a long-term couple in love,” a source tells PEOPLE in its new issue.
But the celebration was just getting started. As his rep exclusively revealed to PEOPLE, Theroux proposed that day – and Aniston, 43, gave him “an extraordinary gift” by accepting. “He’s been dying to do it,” says a Theroux pal of his popping the question. “His friends knew it was coming.”
Immediately after Aniston’s heartfelt “yes!” the couple called their families – including her father, actor John Aniston – and close pals to share the good news.