Multiple Oscar-winner Meryl Streep was the talk of the red carpet at the world premiere of "Florence Foster Jenkins" in London's Leicester Square on Tuesday. The film tells the story of the power of passion and self-belief. In Florence's own words:"People may say I can't sing, but no one can ever say I didn't sing."

'Florence Foster Jenkins' premieres in London

In her latest cinematic offering, Streep plays the titular Florence Foster Jenkins, the legendary New York heiress and socialite who obsessively pursued her dream of becoming a great singer.

The voice she heard in her head was beautiful, but to everyone else it was hilariously awful. Her "husband" and manager, St Clair Bayfield (Hugh Grant), an aristocratic English actor, was determined to protect his beloved Florence from the truth. However, when Florence decided to give a public concert at Carnegie Hall in 1944, St Clair faced the challenge of convincing reluctant pianist Cosme McMoon (Simon Helberg), as well as audiences, of the grande dame's talents.

"Well it's a great story. It's about a real life person who lived in the first part of the 20th century in New York, a socialite who gave a lot of money away to the arts, but her dream was to be a singer," Streep said.

"And with the love of her husband, she was able to believe that she was a singer. But she was a true amateur, she did what she did for the pure love of it. And that's sort of what's beautiful about her."

The U.S. actress has belted out tunes in various musical films, including "Mamma Mia" and "Into the Woods", but this role required her to disguise her singing capabilities.

"What was sort of wonderful about her was how close she came to being good, and when it went off, then's when it got sort of glorious and funny. But it was the attempt, the sort of yearning for it to be good that is the part that's so joyous for me and was fun to do," she said.

Meanwhile the film's ensemble cast admitted that working with Streep was one of the main draws to the project.

"I was at a point where I thought I'd managed to put showbusiness largely behind me, and then suddenly out of the blue, Stephen Frears sent me the script and said, 'Come on, let's do this and Meryl Streep is going to do it'," Hugh Grant said.

"And, you know, it was such a good script, such a good part for me, and the fact that Meryl Streep, possibly the greatest film actress ever, was in it, I couldn't say no."

"I just want to prove that I got to hang out with Meryl Streep and Hugh Grant, so I think that this movie proves it...I'm so beyond honoured to have gotten to do it, and play music with Meryl and do this thing. It's crazy," said Simon Helberg.

Despite not sharing much screen time with Streep, actress Rebecca Ferguson said the production felt like "acting school".

she said:" I feel I've been in a Meryl Streep film and that's enough. I know that I would stay, when I had wrapped my day, and I knew she had a performance on stage singing, I'd just go in the back and just watch her. It's like acting school," she explained.

"Florence Foster Jenkins" opens in the UK on May 6 and in the U.S. on August 12.