Guillaume Canet was worried about showing favouritism to partner Marion Cotillard when filming 'Blood Ties.'

The 40-year-old filmaker didn't want the other cast members to see Marion - who plays Monica in the adaptation of the French novel of the same name - as his partner, but wanted them to give her credit as an actress in her own right.

He told Telestar: ''On set, I didn't want to show any favouritism because I was worried the rest of the crew would think I was talking to her primarily as my partner and not as an actress. But something magical happened between us: trust. It was the best present she could have given me.''

Meanwhile, she was worried about making his vision play out perfectly on screen.

She explained: ''I trust him 200 per cent! Contrary to what Guillaume has just said, he was always very fair when it came to me. My main concern was to satisfy his vision. And when I could see he wasn't happy on set it affected me deeply.''

The pair still manage to find time to themselves when they're at home.

Although Marion wasn't keen to talk about their romance, claiming: ''We never talk about our private life because...''

Guillaume revealed his romantic side, saying: ''You could at least say that I'm a very romantic person at home!''

Before Marion added: ''OK, I can say that - it's true!''