The inventors

Robert De Niro at La Grenouille for Twentieth Century Fox's Joy Photo: Anne-Katrin Titze

Bradley Cooper, according to his mother, had the greatest gift, and director David O. Russell recalls being a media mogul at an early age. Robert De Niro spoke about his own father, Robert De Niro Sr., in the film Peggy Guggenheim: Art Addict and told me he was nothing like Rudy in Joy. The trio has worked brilliantly together, along with Jennifer Lawrence, twice before, in Silver Linings Playbook and American Hustle, and now, about the inventor of the Miracle Mop. Joy is supremely influenced by her mother and grandmother, played by Virginia Madsen and Diane Ladd.

Bradley Cooper with mum, Gloria Campano Photo: Anne-Katrin Titze

Bradley admits he still misses The Elephant Man with Alessandro Nivola and Patricia Clarkson, while David O. Selznick and Jennifer Jones remain a mystery to him. When he arrives with a chic blonde, dressed in black, I ignore him and go straight up to her.

Anne-Katrin Titze: Did Bradley invent anything as a child?

Gloria Campano: Invent? Happiness and joy!

Bradley Cooper: There you go!

AKT: Do you remember inventing anything else?

BC: I don't know. How are you doing?

AKT: Fine. I have done quite a few features with Alessandro, and often spoke of Elephant Man. Do you miss Elephant Man, already after half a year?

BC: Yes! We did 280 shows.

Robert De Niro on Isabella Rossellini as Trudy: "She's a little aggressive. Maybe she was that way with Morris, too?"

AKT: Your part in Joy is very different from the previous two roles with David O. Russell. You are very serious. It's quite a turnaround from…

BC: … Richie DiMaso [American Hustle] and Pat Solitano [Silver Linings Playbook]. But that's what David does. He always … I think that's part of the reason why people come back and back because you're sure that he is going to take you to different places. And he never wants to repeat anything. It's been thrilling to work with the same actors in completely different capacities with different characters.

AKT: You have one line about the American dream - and I wondered if there was an inside joke there. Your character gives the example of David O. … Selznick and Jennifer … Jones?

BC (his eyes widening): No! That's so funny. You have to ask the director/writer that question! You have to ask him.

Joy lunch at La Grenouille organised by Peggy Siegal Photo: Anne-Katrin Titze

As he dashed off after the lunch, I had a quick exchange with Robert De Niro.

Anne-Katrin Titze: I was stunned by what you said in the Peggy Guggenheim film. Both your parents' artworks were exhibited in Guggenheim's Venice Museum?

Robert De Niro: Yes! I think my father was. I don't know if my mother was.

AKT: The father you play in Joy is really unlike any other I could think of. Did he remind you of any other kind of father you know? I don't mean yours.

RDN: No, not mine. My father wasn't…

AKT: Any filmic fathers of cinema, maybe? How would you describe Rudy Mangano?

RDN: He is a guy - he is a loving father, he's just ….

AKT: … incapable of being a father?

Joy US poster in the Flatiron district of New York Photo: Anne-Katrin Titze

RDN: Well, in a certain way. And also, Isabella [as Trudy] sort of took advantage, you know, pushed him. She's a little aggressive. Maybe she was that way with Morris, too? You know, Morris, her [dead] husband.

AKT: You two have great chemistry in Joy. I love how you play off each other.

RDN: Yeah, no, no, she was terrific.

Joy Mangano, who gave the world the Miracle Mop, started inventing young.

Anne-Katrin Titze: Did you invent anything when you were little?

David O. Russell: I invented, I made a whole TV station in my house. I took a pane of glass that my parents were throwing out that I cut myself. I don't know if that counts as an invention. I had a whole control room. I took Clorox bottles, empty Clorox bottles and made them into puppets by turning them upside down and cutting out like a mouth with a wire. I did a whole thing like that. And a thing out of hangers so I could hang all my toys at the back of the door. I cut off the hook parts of the hangers and strung them together.

Joy opens in the US on December 25 and in the UK on January 1, 2016.