Director Lulu Wang has told of her initial reluctance to cast Awkwafina in her new film The Farewell.

The film-maker said at first she did not want to cast the Crazy Rich Asians actress in the movie, which is based on her own experience of finding out her grandmother was terminally ill and then learning her family in China intended to keep the news from her.

Wang told the PA news agency: “We cast her before Crazy Rich Asians came out, before Ocean’s 8, she was not famous, I knew her from her rap videos on YouTube.

Awkwafina as Billi (A24/Entertainment Film/PA)

“I knew she did some comedic acting but I hadn’t really paid that much attention and hadn’t seen a lot of those films when I met her, so it was really just that I was worried that my producers only wanted her because she’s an influencer.

“But her audition tape is what really convinced me. She sent in a self-taped audition and the tape was incredible, I saw her performance on the tape and just realised that she has tremendous range.”

The film stars Awkwafina as Billi, who was born in China but has been raised in the US. She returns to Changchun after her grandmother, Nai Nai, is diagnosed with terminal cancer but the family has decided not to tell her.

Wang first told the story on an episode of the hit podcast This American Life, before making it into a film.

She said: “I always wanted it to be a film – as a film-maker that is my natural inclination, to see a story as a film – but I pitched it around town and was not able to find producers or financiers and that is when I set it aside for quite a while.

“When I met a producer from This American Life it was always in the back of my head, trying to find a way to tell this story, so I brought it up to him and we ended up doing it for This American Life, and then producers came to me after hearing it on the radio saying, ‘Have you ever considered making this a film?’ Funny you should say that! So it worked out.”

Wang said retelling the story for the big screen changed the way she felt about her family’s decision, adding: “It gave me a lot more compassion because throughout the process of making the film I had to interview them and ask them questions and really come to have a greater understanding.

Awkwafina as Billi and Zhao Shuzhen as Nai Nai (A24/Entertainment Film/PA)

“I think that is what was so great about this process, that it wasn’t just like I knew the story, I knew the film I had to make, and I knew what I wanted to say, it was a true exploration.

“I was truly torn between my family and respecting their decision, and what I felt to be unethical, and so in the exploration of making the film and exploring both sides of it, I think I came out with a much more balanced view of the two sides.”

She also cast her grandmother’s sister to play herself in the film, saying: “In the beginning we just didn’t know if she could act, as much as I loved her.

“I initially thought about casting her to play Nai Nai herself but because she doesn’t act it’s much harder for her to play a different character, and so then I thought she should just play herself – instead of her playing her sister and an actress playing her, I will just have her play herself.

“It took a few auditions before I could realise that she could do it because she kept trying to act and then when I said ‘just be yourself, just talk to me like you would normally’, she did that… all of the emotions came out, because she was talking about her real life, her real experiences.”

The Farewell is released in UK cinemas on September 20.