Regency-era London took over the British capital's Leicester Square on Friday as the "Queen Charlotte" cast premiered the first spin-off from hit Netflix period drama "Bridgerton" dedicated to the fan favourite character.

"Queen Charlotte: A Bridgerton Story" is an origin story of the "Bridgerton" monarch, explaining her rise to power and love life.

The six-episode series follows two seasons of Regency-era "Bridgerton", which became a global phenomenon when it was released in 2020 and won praise for its diverse cast.

With two timelines, Golda Rosheuvel reprises her "Bridgerton" role as the monarch while India Amarteifio plays the young Queen Charlotte.

"I think where we left her in 'Bridgerton', a lot of people had questions. We see that she's the matriarch so to say and the kind of highest ranking officer in society but we don't really know why," Amarteifio told Reuters.

"(Audiences) know that there's this beautiful love connection between her and husband...but also in 'Bridgerton' it's so diverse and beautiful, there's lots of different people coming together and people wanted to know why and I think 'Queen Charlotte' answers that."

Showrunner Shonda Rhimes, also behind "Bridgerton", said it was "very exciting" to make Queen Charlotte the centre of her own story.

"That woman that we see in 'Bridgerton', like all her power, her style, the way she carries herself - I kept wondering how she came to be and it was a really simple thing to write this story because it felt like we were just watching a woman earn her power and seeing a great love story," she said.

One major plotline is 'The Great Experiment" - which looks at how to desegregate the high society by marrying the monarch, King George, to a Black woman, Charlotte.

"What's so brilliant about this series 'Queen Charlotte' is that it's not colour blind casting in any way, it's purposeful," said Corey Mylchreest, who plays a young King George.

"It's brilliant what 'Bridgerton' did in terms of diversity and representation but I think it's even more powerful when you show the work that has to go to achieve that, and I think that's what this show does."

"Queen Charlotte" begins streaming on May 4.