Hannah was called to the Bar in 2001. She initially practised at the independent bar, then as a prosecutor for the SFO and FCA. She joined Peters & Peters in 2010 and became a partner in 2014.

She manages high-profile, complex litigation often involving the SFO, FCA or other UK or global enforcement agencies. She has advised numerous corporate entities, including financial institutions, as well as senior executives, directors and high net worth individuals. She is highly regarded for her legal and project management skills. In Chambers and Partners 2021, she is described as "excellent and extremely able" with "the ability to win the trust of her clients".

Hannah is recognised as a leading lawyer in her field. She is listed as a thought leader in Who's Who Legal for investigations and business crime defence for corporates and individuals. She is named as a leading individual in Legal 500 for regulatory investigations and corporate crime, white-collar crime individuals and contentious financial services. She is also ranked in Chambers & Partners.

In 2017, Hannah received the Employed Bar Award for Outstanding Achievement by a Barrister in a Corporate Organisation or Solicitors' Firm. In 2015, she was named as one of the world's leading female investigative lawyers in Global Investigations Review.