Heather McMahon

Call: 1999

Heather’s areas of practice are professional liability, commercial law, professional discipline and medical law.

Her principal area of practice is professional liability claims and she is ranked as a leading junior in this area by Legal 500.  She acts for and against a wide range of professionals, with particular experience of claims against lawyers, surveyors, valuers, and financial professionals. Heather also has a busy commercial law and professional disciplinary practice. She appears regularly in the High Court, County Court and specialist tribunals.

Before joining Chambers, Heather worked for the Government Legal Service for eight years, where she gained wide experience in public and regulatory law. She has an in-depth understanding of the demands on lay and professional clients, and takes a commercial and client-friendly approach to litigation.

Professional Liability

Heather has acted for claimants and defendants in claims involving all manner of professionals. She has particular experience of claims against lawyers, surveyors and valuers, and financial professionals. She is frequently instructed in large, document heavy cases which are particularly legally or factually complex.


Heather has extensive experience of claims against solicitors, arising out of most areas of legal practice. Her work includes claims arising from litigation gone wrong including lost litigation and undersettlement claims, conveyancing and lender claims, claims arising from the conduct of family proceedings, including matrimonial finance disputes, and claims arising from non-contentious transactions, including contracts, wills and other property and trust disputes. She has also acted in a number of cases against barristers, including contribution claims.

Heather has considerable experience of related policy coverage disputes, including aggregation and dishonesty issues.

Her current and recent work includes acting for the defendant solicitors and former executors on a £20m contentious probate claim (with Francis Bacon), acting for a lender in claims against its former solicitors in relation to various high value loans (some with William Flenley QC; others as sole Counsel), and acting as sole Counsel on a number of substantial claims against solicitors arising out of allegedly inadequate advice given to purchasers in residential property developments.

Property Professionals

Heather is frequently instructed in claims against surveyors and valuers, typically arising out of alleged failures to detect or report on problems in properties and inadequate valuations. She has also acted in numerous claims against estate agents and property managers.

Financial Professionals

Heather has acted in a wide range of claims involving financial professionals, including accountants, IFAs, insurance brokers and insolvency practitioners.

Construction Professionals

Heather has acted in various claims against architects and contract administrators, including TCC claims.

Heather has a growing medical law practice. She has appeared in and advised on a wide range of claims, including delayed diagnosis, missed diagnosis and consent claims.

Heather has considerable experience of professional regulatory and disciplinary claims. She is regularly instructed to represent registrants before the Nursing and Midwifery Council and has also acted in Health and Care Professions Council cases. The cases in which Heather has appeared often involve allegations of serious misconduct, including patient deaths, dishonesty, abuse and assault. She also has considerable experience of cases alleging lack of competence and health issues.

Heather is regularly instructed to advise on a broad range of commercial matters. Her cases involve a variety of commercial legal issues, including contractual claims, commercial fraud claims, interim relief claims, business and property disputes, shareholder disputes, breaches of directors’ duties, breach of trust and breach of fiduciary duty claims. In addition, she has considerable experience of insurance policy coverage disputes linked to her professional liability practice.

Her current and recent work include advising on High Court proceedings under ss.66 and 67 of the Arbitration Act 1996, several cases involving allegations of actual or suspected civil fraud, acting (with William Flenley QC) on a breach of fiduciary duty claim, and acting for a Formula One engineer alleged to have taken confidential data belonging to his employer.

Heather acts for claimants and defendants in all aspects of personal injury law, including employer’s liability, occupier’s liability, criminal injuries and public liability claims.

She has considerable experience of claims arising out of road traffic accidents, including claims involving allegations of fraud, indemnity issues, MIB claims and credit hire.

Heather also has considerable experience of public law and business regulation, gained during her time as a Government lawyer. She advised a wide range of central Government departments, working on business regulation, including insolvency and insurance issues, criminal justice, education and healthcare.

“She is super-sharp and thorough. A good communicator who works very hard.” Legal 500, 2022

“A very strong junior who works well in a team. She has an extraordinary ability to distil key relevant facts from vast amounts of material.” Legal 500, 2021

“Very good on complex matters”  Legal 500, 2020

Specialist areas: professional negligence, commercial litigation, personal injury, regulatory and disciplinary, public law.

University College, Oxford – BA (Hons) Jurisprudence: First Class


  • Pegasus Scholarship from the Inns of Court to the John Marshall and Lewis F. Powell Jr. American Inns of Court, Richmond, Virginia, 2004
  • Middle Temple Harmsworth Entrance Exhibition, 1998


  • Government Legal Service, 2001-2009
  • Judicial Assistant to Sir Andrew Morritt, Vice-Chancellor of the Supreme Court, 2001

Publications and Lectures
Heather regularly presents lectures and talks to clients in her areas of practice.

She assisted with research for Flenley and Leech, The Law of Solicitors’ Liabilities, fourth edition, 2020.

Heather is an enthusiastic spectator of most sports and an occasional participant in a few. In her spare time, she enjoys cooking, travel and photography.

ICO Data protection registration number: Z2003875

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