Leonia Chesterfield

Expertise

Leonia specialises in competition law and antitrust disputes including collective proceedings in the UK’s Competition Appeal Tribunal (CAT).

Leonia joined the firm in 2024. In recent experience, Leonia has worked on defending large-scale antitrust litigation in the tech sector in addition to acting on the claimant side in collective proceedings.

Formerly, Leonia worked for several years at the Competition and Markets Authority where she worked across its Litigation, Mergers and Policy teams. Her broad experience spans regulatory investigations, UK merger control, competition and consumer law.

Leonia has been named as a recommended lawyer for Competition Litigation in the Legal 500 (2025 and 2024 editions). She holds an MA in Competition Law (King’s College London) and dual law degrees from King’s College London and the Sorbonne, France.

How do you help clients?

I help clients in relation to their competition law requirements and antitrust disputes. This includes those wronged following anti-competitive conduct who may wish to seek redress, including through collective proceedings.

Experience

1. Advising on large-scale competition litigation disputes in the tech sector.
2. Assisting clients with a range of competition law requirements, including merger control and CMA investigations.
3. Helping clients in relation to competition compliance including dawn raid support.
4. Acting on a consumer law test case for overdraft charges against the UK’s leading banks (up to the Supreme Court) while working for the competition authority.
5. Defending regulatory and infringement decisions in the Competition Appeal Tribunal.