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About Mairi McMartin

Mairi is counsel in our Antitrust, Competition and Trade team based in Brussels. Her practice spans all aspects of EU, UK and international competition law, as well as foreign investment screening and the emerging regulation of digital markets.

She has extensive experience of complex cross border merger control, including in-depth review and remedies negotiations before the European Commission, the UK’s Competition and Markets Authority and authorities in other jurisdictions.  She also manages the growing impact of foreign direct investment on deals. 

Mairi’s behavioural practice covers investigations into anti-competitive agreements and abuse of dominance, global antitrust compliance and best practice, and competition and regulatory issues in litigation proceedings.  

She has recently been advising on emerging digital regulatory regimes including the EU’s Digital Markets Act.

Mairi works across a range of industry sectors, with a particular focus on innovative sectors such as technology, life sciences and industries in transition.

Mairi speaks English, German, Dutch and French.

Recent work

Mairi’s experience includes advising:

  • A gatekeeper on all aspects related to the EU Digital Markets Act.
  • A US cloud computing and virtualization technology company on the EU merger control and global FDI aspects of its USD 61 billion acquisition by a global technology company, which was subject to in-depth merger control and FDI investigations in the EU, the UK and around the world.
  • An interested third party in relation to the EC’s investigation and subsequent prohibition of Illumina’s acquisition of  GRAIL and related proceedings.
  • A global communications company on the merger control and FDI strategy in relation to a proposed 3 to 2 transaction with a deal value of approximately USD 10 billion.
  • A US energy company active in the oil and gas sector on the merger control and FDI aspects of its USD 700 million joint venture with a European energy company active in the oil and gas sector.
  • A global supplier of food service equipment on the merger control and FDI aspects of its USD 4.8 billion deal with another global food service equipment supplier, including EC and UK CMA Phase I remedies.
  • A multi-national media and information services conglomerate on the merger control and FDI aspects of its USD 1.15 billion acquisition of two price information businesses, which were divested to a suitable buyer following remedies decisions by the EC and the UK CMA in a high profile transaction.
  • A supplier of dialysis services on the merger control and FDI aspects of its global JV with a leading medical device supplier.
  • A global healthcare company on the merger control and FDI aspects of its USD 1.5 billion acquisition of a leader in advanced surgical ultrasound.
  • A US diagnostics company on the merger control and FDI aspects of its USD 6 billion acquisition of a global in vitro diagnostics company.
  • A long-running antiturst investigation in the financial services sector and successfully negotiating article 9 commitments with the EC.
  • A number of investment firms and PE clients in relation to the merger control and FDI aspects of various transactions across a broad range of sectors.
  • clients in relation to all aspects of the UK National Security and Investment Act, including in-depth reviews.



  • Solicitor, England and Wales
  • Member of the Brussels Bar



  • University of Glasgow (LLB) with Erasmus at the Freie Universitaet Berlin
  • Legal Practice Course, Oxford Institute of Legal Practice
  • Postgraduate Diploma in EU Competition Law, King's College London