Despite their distance, both had made efforts to ensure the relationship was still going strong. In October, Vaughn, 36, threatened to sue several tabloid newspapers that alleged he was seen kissing a mystery blonde and had ended his relationship with Aniston, 37. The actress also shot down rumors of a rift on Oct. 11 when she told Oprah Winfrey that the two were still together.
Aniston visited Vaughn in London in late October after spending nearly a month apart. The two took in the London sights and caught a matinee showing of the musical Wicked. The actress returned to L.A. a few days later.
The couple began dating in the summer of 2005 while working on The Break-Up in Chicago. "She's awesome," Vaughn told PEOPLE that June. "She has just a wonderful warmth and likeability about her."
Rumors of a romance began to swirl almost immediately when they started filming – especially after the costars appeared touchy-feely at the film's wrap party last year – but both insisted they were just friends.
Aniston told Vanity Fair, "I adore Vince Vaughn, but I'm not going out with Vince Vaughn." Vaughn told Katie Couric on the Today show at the time, "(Jen's) been great, and we've been having a great time shooting the movie. But that's really been the extent of it."
But by that fall they were back in Chicago, near Vaughn's Lake Forest hometown, where they were spotted kissing and cuddling at various bars and restaurants – and even having lunch with his mother, Sharon, and stepfather.
Though they never publicly discussed their romance, the couple were soon deflecting wedding rumors. In April, Aniston called in to The Oprah Winfrey Show to deny a tabloid report that Winfrey was planning an $8 million wedding for her and Vaughn.
"(The rumors) are so unbelievable," Aniston told Winfrey. "It sounds like you're giving me Santa Barbara." Asked if she had anything to announce, Aniston said, "No wedding, no moves, no, no."
A few weeks later, Vaughn himself joked to Winfrey, "I'm expecting a pretty good band for $8 million." He also told the talk-show host, "Jennifer's great. She's one of my favorite people. ... She's just really smart and funny and easy to be with – very considerate. She's great."
This past summer, the couple traveled to The Break-Up premieres all over the world, and, although they avoided being photographed together on the red carpet, were seen taking a romantic boat ride in Paris, catching a Cubs game in Chicago and visiting an aquarium in Sydney.
"Vince and Jennifer are the real thing," a Vaughn friend told PEOPLE at the Los Angeles premiere of The Break Up in May. "They're both in a really great place."
Aniston herself said on the red carpet that night, "I'm just happy. There's no reason to be anything else, is there?"
But in August, Aniston told PEOPLE that published reports that the couple were engaged were "insane" and that "people are getting fed a lot of bull."
After doing a well-received stint in the 6th Annual 24 Hour Plays on Broadway benefit in October, Aniston has been back in L.A. Vaughn will be shooting Fred Claus in London through this month.