Director Marshall admits the chemistry on the set, that he'd experienced with the pair while making Pretty Woman with them a decade earlier, was difficult to come by - because the actors had become conscientious superstars.
The celebrated filmmaker says, "They suddenly both had cellphones and they put that on their ear and that was it - they were very busy.
"Richard, of course, is very close to the Dalai Lama... and Julia was really helping orphans in Jamaica and so once in a while I had to say, 'Anybody wanna make a movie here?' I was so afraid to interrupt them because I didn't wanna hurt the charities. They were more pre-occupied."
And Marshall reveals some of the film's romantic scenes had to be shot on days his stars wanted to be elsewhere: "There was that one day that the schedules didn't work out and they were both upset - they wanted to go some place. So they couldn't look in each other's eyes.
"But nothing stops me. I got a kite... and they're both looking up and it looks like they're in love.
"The next day they were happy. In the end titles of that movie there's a scene in the snow that they were clearly so affectionate with each other."