Rising star Hannah will join the cast of the Netflix show when it returns to the platform after Ruby was forced to quit due to taking on the lead of Lockwood & Co.
She will portray Francesca, who is described as a bit of a mystery within her chatty, extroverted family.
Despite her reserved nature, she goes along to get along when it comes to social affairs, fortified with a dry wit and pragmatism that confound the fickle ton yet seem to draw attention when she least desires it.
Hannah went straight into her first acting job from school, playing one of the series leads in Find Me In Paris, continuing the role in a further two seasons.
She also featured in a recurring role in two seasons of the highly popular series Harlots alongside Lesley Manville and Samantha Morton.
Bridgerton season three was announced earlier this year, along with season four.
The third book, titled An Offer From a Gentlemen, is about Benedict and Sophie, while the fourth book, called Romancing Mister Bridgerton, is about Colin and Penelope.
However, she added: ‘We’re not necessarily going in order but we are going to be seeing each of the siblings and their stories.’
So, we will just have to wait to find out which couple season three will focus on.
In March, it was revealed that the ostentatious Queen Charlotte is getting her own spin-off show.
The regal monarch, played by Golda Rousheuvel, will have her own prequel series, focusing on her past, childhood, and love life.
We’re not quite used to seeing Queen Charlotte in a romantic, youthful way, as all through the first two seasons her scary demeanour left other characters in awe and fear.
It won’t just be the young Queen Charlotte who will feature, as beloved characters Violet Bridgerton (Ruth Gemmell) and Lady Danbury (Adjoa Andoh) will have their own histories uncovered.
Bridgerton is available to stream on Netflix.