Definitely. It takes cues from actual happenings and tells a story rooted in truth. Some details might be fictionalized for dramatic effect, but the core is based on reality.
Katharine Gun is the key character. There are also other characters like her lawyers who play important roles in the story. They help her in her fight against the charges she faces for leaking the official secrets. And there are characters representing the government agencies who are on the other side of the story, trying to prosecute her.