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Zachery O'Brien, Associate, Corporate

Zachery O'Brien

Managing Associate

Personal Profile

Zac is a Managing Associate in the Competition group in the Innovation department.

Zac has strong experience of cases involving competition litigation, competition advisory, public procurement  and judicial review cases. He advises a number of high street and online retailers in relation to competition matters. He also has experience advising on cases involving the sports, pharmaceuticals and transport sectors.

Zac is on the Committee for the Junior Competition Network. He is also part of Mishcon's Disability Committee and regularly volunteers for the Guide Dogs for the Blind Association.

Key Experience


  • Advising Asda, Currys, Iceland, John Lewis, Sainsbury's and Wilko in relation to claims against the European Trucks Cartelists in the English High Court.
  • Advising Sainsbury's in relation to its claims against Mastercard for anticompetitive overcharges of interchange fees at first instance in the Competition Appeal Tribunal, on appeal in the Court of Appeal, and on appeal to the Supreme Court. 
  • Advising a major European electronics retailer on strategic dispute resolution options aimed at securing significant recovery of cartel damages without litigation.
  • Advising a director in relation to allegations of competition law breaches.
  • Advising a sports body in relation to an alleged abuse of a dominant position.

Public Procurement and Public Law

  • Representing parties in judicial reviews in the High Court and Supreme Court.
  • Advising a party who issued proceedings in relation to a tender for library services.
  • Advising a tenderer in relation to a procurement involving the competitive dialogue process for a contract to provide security solutions.
  • Advising private sector developers on land agreements in relation to the Public Contract Regulations 2015.
  • Advising a financial services firm in relation to its challenge to a procurement involving the open procedure.
  • Advising an employment agency in relation to a challenge to a contracting authority not using a framework agreement when awarding call-off contracts.

Career History

Managing Associate, Mishcon de Reya LLP
Associate, Mishcon de Reya LLP
Trainee, Pinsent Masons LLP


PGDip (Public Procurement Regulation in the EU and its Global Context), Kings College London

MA (European Competition Law), Kings College London 

Legal Practice Course, The University of Law (Moorgate)

LLB (Hons), City University London          

BA (Hons) (History), The University of Sheffield   

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