Kate Gartside wrote the script and producers are Sophie Balhetchet for Cougar Films and Tristan Orpen Lynch for Subotica. The Irish Film Board and Northern Ireland Screen supported the film's development.
The story follows the life of Northern Ireland civil rights campaigner Bernadette Devlin. She was the youngest woman MP elected to British parliament at age 21, and she later had to shield her children from assassins' bullets.
Gartside previously wrote Lilies and No Angels. 'Researching this young woman left me humbled at her courage, outraged on her behalf, convinced that her story must be told,' she said.
Walsh, who has directed Song For a Raggy Boy and the recent Samantha Morton starrer The Daisy Chain, said: 'I have been fascinated by this woman for 20 years and more than ever the time is right to tell her amazing story in film.'
She said Hawkins was the right woman for the role - they will reunite after working together on BBC TV's Fingersmith. 'Sally's bravery and courage, as an actress who commits herself totally to a role, is one of her greatest qualities. She has that amazing ability to lose herself and totally become the character she is playing,' Walsh said.
'I am honoured to be playing the role of a woman who was such a force in the battle for civil rights and to be working again with Aisling who is an inspiration.' says Sally Hawkins.
Producer Sophie Balhetchet adds: 'This is the first film to tell the turbulent politics of Ireland explicitly from the point of view of a woman. Sally Hawkins is an extraordinary actress who will bring an immense strength and passion to the role.'
Balhetchet founded London-based Cougar with Lynda La Plante and the company also has the feature version of La Plante's Widows in development with writer Andrea Gibb.
Ireland-based Subotica has previously produced Night Train, On The Nose, Song For A Raggy Boy and Small Engine Repair.