‘Two-week rule’ that is the success behind Robert Downey Jr.'s 19-year marriage

Robert Downey Jr. has been married to his partner for the best part of two decades, and a 'two-week rule' has been credited as the couple's secret.

Downey Jr met Susan Downey in 2003 on the set of Gothika, with the actor starring in the project alongside Halle Berry.

Susan, on the other hand, was a producer on the movie through her job with Silver Pictures - but it certainly wasn't love at first sight.

The film producer told The Hollywood Reporter in 2014 how she found Downey Jr 'interesting but weird'. I mean, talk about backhanded compliments.

Susan also conceded she didn't want to date the star of the film she was working on, but she later agreed to go on a date with the now 60-year-old - and the rest as they say is history.

Robert Downey Jr married Susan in 2005 (MICHAEL TRAN/AFP via Getty Images)

Many will wonder how the pair have maintained such a successful marriage, thankfully Susan has revealed all.

Susan explained that the pair have a crucial rule; they do not go longer than two weeks without seeing each other.

“We do have a two-week rule, which often feels too long, but we don't go more than two weeks without seeing each other and the family being together,” Susan told People.

“Fortunately, we prefer to be a traveling circus when we can be," she continued.

The couple try to stick with the 'basic rule' but sometimes life can be 'oddly unpredictable' so they don't think 'too far ahead'.

“Someone might get sick, or there might be a shutdown, or this or that. So you just have to have some basic things in place, and then you have to be willing to flow with the rest of it,” she added.

The couple follow a 'two-week rule' (Steve Granitz/FilmMagic)

Susan went on to say she was fortunate that her job as a producer doesn’t require her to be in front of the camera so she can be more flexible when it comes to seeing her family.

Susan added: “The good news is I'm not in front of the camera, and so as a producer I end up with a little bit more flexibility in terms of location, of where I would need to be.

“I really admire and have a lot of empathy for couples who both have to be in front of the camera, because you get stuck and you have to make those choices.”