Indian filmmaker Sanjay Leela Bhansali was able to draw on his own childhood memories to make "Gangubai Kathiawadi", a blockbuster adaptation from the book "Mafia Queens of Mumbai", about Gangubai, a sex worker turned women's rights champion.

The acclaimed director's first collaboration with celebrated actress Alia Bhatt, which premieres at the Berlin Film Festival on Wednesday, chronicles Gangubai's rise from vulnerable sex worker to a powerful figure in the city's red light district.

"I was born and brought up just two lanes away from where she lived, the brothel where she lived, and I spent a lot of time of my childhood passing through those areas," he said. "When I read the book, I was very moved," Bhansali said.

Based on a chapter from S. Hussain Zaidi's book, the film was beset with difficulties almost from the start.

"We were hit with the pandemic right in the middle of the shoot," she said. "They had to create like an industrial shed around the set so that it would not get rained out ... the set went through two cyclones."

Bhatt, making her third Berlinale appearance, said her performance was born out of long conversations with Bhansali - who had a very specific vision for which the star had to deepen her voice.

"He wanted me to ... get a base in my voice because I have a bit of a high-pitched tone, especially when I speak with energy and it sounds a bit childish," Bhatt said. "He wanted weight. He wanted intensity."

Bhansali is known for his song and dance sequences but in "Gangubai Kathiawadi" the filmmaker wanted authenticity and performances that would bring the story forward, said Bhatt. adding it made the film stand out from his earlier work.

"Gangubai Kathiawadi" will be released in theatres on Feb. 25.