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Kate Macmillan

Kate Macmillan


Kate Macmillan is a consultant in the cyber and data security practice in the intellectual property group.



Kate advises clients on operational resilience and breach prevention as well as upon all aspects of incident response and the aftermath of incidents, including regulatory investigations and litigation brought under data protection, privacy and information law.

Kate is a solicitor advocate with rights of audience in all civil proceedings.

Kates' experience includes:

  • Leading PwC's cyber and forensics teams on multi-jurisdictional breach response engagements
  • Building PwC's personal data breach planning runway (Breach Readiness Assessment tool covering multiple domains including law, media and cyber security guidelines; Personal Data Breach Legal Playbook; Personal Data Breach war gaming; Personal Data Breach retainer services)
  • Leading on a key element of the Information Commissioner's formal investigation into the use of data analytics in the political sphere
  • Leading on a high profile inquiry into corruption in global sport (which included contentious data issues)
  • Advising international clients, including a global cloud human resources planning provider and the UK's largest power station upon data protection and cyber law
  • Leading on reputation management issues for PwC and its clients
  • Advising a leading transportation company with an annual turnover of £900m upon its GDPR compliance programme
  • Acting successfully for the NHS in defence of a defamation, data protection, harassment and breach of the Equality Act claim
  • Advising the General Secretary of a prominent trade union and the trade union in a range of matters
  • Acting for individuals and corporates on defamation, privacy, harassment, confidence, data protection and intellectual property matters, including acting successfully for the child of a high profile politician in a High Court privacy case against Associated Newspapers
  • Part of a four partner team acting for victims of phone hacking using the Group Litigation Order procedure
  • Acting for a Swiss corporate to bring a successful multijurisdictional harassment claim on behalf of its leadership using the Representative Action procedure
  • Acting successfully in various intellectual property matters including for leading fashion brands such as Liberty.




Immediately before joining Herbert Smith Freehills Kate was a Director at PwC, where she led the contentious data privacy and cyber security legal practice.

Prior to that she was a partner in Collyer Bristow's IP and Media teams.

She trained and worked for almost a decade with leading reputation management and litigation firm, Carter-Ruck.


  • "Macmillan attracts praise as a real star in the data privacy space, who is building a formidable team around her; she is a very clever litigator with huge experience, and is masterful at managing tricky cases." Legal 500, 2017
  • "Kate Macmillan is outstanding." Legal 500, 2016
  • "Kate is a well-regarded dispute resolution partner demonstrating expertise handling reputation management matters for corporate brands. Clients describe her as calm in a crisis – she works extremely hard and diligently and is reassuring to people in the eye of the storm" Chambers and Partners, 2015
  • "Kate is a prominent reputation management specialist. She draws considerable praise from clients who note she is calm in a crisis, provides clear advice and does not bog me down with legalese." Chambers and Partners, 2013.