Gerard Depardieu was so hurt by the release of his son's autobiography last year, filming on the movie he was making was delayed as the veteran actor started drinking heavily.
Depardieu was shooting 36 Quai des Orfevres when Guillaume Depardieu unveiled Tout Donner, a book which negatively portrayed his 57-year-old father.
Director Oliver Marchal says: "He was brilliant because he stayed on the set and I looked after him like a little boy.
"There are some actors who are difficult. With him, you forgive him, because for me that helped the film, even if it took longer because there were one or two days when he couldn't stay upright - he was dead drunk - and we had to keep filming.
"And of course that helped for the character, but at the same time he's someone with an enormous heart. I couldn't hold it against him."