Heather McMahon

Call: 1999

Heather specialises in professional liability and related insurance disputes, commercial litigation, and regulatory work.

Described as “exceptionally talented” and “client-friendly”, Heather has been ranked as a leading junior for professional negligence by Legal 500 for several years.  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 substantial experience of professional indemnity insurance disputes.  She appeared with William Flenley KC in the Court of Appeal and Commercial Court in Discovery Land Company v Axis [2024] PNLR 16, the leading case on the meaning of the dishonesty exclusion in the solicitors’ Minimum Terms for insurance.

Professional Liability

Heather acts 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.

Lawyers

Heather has extensive experience of claims against lawyers, 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 corporate transactions, tax planning schemes, and wills and trust transactions.  

Heather also has experience of advising on the professional conduct of solicitors, including matters relating to the Solicitors’ Accounts Rules and confidentiality issues.

Her current and recent cases include:

  • defending a lost litigation claim arising out of failed employment tribunal and civil proceedings, said to be worth more than £7.5m
  • acting for solicitors in an application by their former client to restrain the solicitors from acting for the former client’s opponent in subsequent litigation (with William Flenley KC)
  • various claims arising out of failed property investment schemes in the UK and abroad
  • acting for solicitors and former executors on a £20m contentious probate claim (with Francis Bacon).

Property Professionals

Heather is regularly instructed in claims against property professionals, including claims against building surveyors, valuers, estate agents, and property managers.

Financial Professionals

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

Construction Professionals

Heather has experience of a number of claims against architects, quantity surveyors and engineers of various different specialisms, typically relating to residential property development.

Heather often acts insurance coverage disputes, largely but not exclusively in relation to professional indemnity insurance. She has particular experience of advising on dishonesty and aggregation issues. She acted (with William Flenley KC) in the Court of Appeal and Commercial Court in Discovery Land Company v Axis, a high profile coverage dispute arising out a former solicitor’s fraud (see above). She has also been instructed on various arbitration proceedings about solicitors’ professional indemnity insurance and in arbitration claims about after the event insurance cover.

Heather is instructed to advise on a broad range of commercial matters, including contractual claims, claims arising out of fraud and deceit, business and property disputes, shareholder disputes, and claims for breach of trust and breach of fiduciary duty.

Her current and recent work includes several cases involving allegations of actual or suspected fraud, recovery and enforcement claims, and claims for urgent relief.

Heather has considerable experience of professional disciplinary work.  She represented registrants before the Nursing and Midwifery Council for many years. Her work in this area includes the successful defence of allegations of clinical misconduct and dishonesty regarding the condition of a baby at birth, which turned on the successful cross-examination of the various medical experts, and the successful defence of a registrant whose admitted medication errors were alleged to have contributed to the death of a patient.

Heather also has experience of advising on solicitors’ regulatory obligations and on applications for disclosure against the Solicitors Regulation Authority.

"Heather is an exceptionally talented, client-friendly, very capable thorough. She is measured and calm, very organised and on her feet she is very impressive." Legal 500, 2024

"Very hard working, thorough, dedicated and intelligent." Legal 500, 2023

“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

Heather has a first class degree in law from University College, Oxford.  

Before joining Chambers, Heather worked for the Government Legal Service for eight years, where she gained extensive experience in public and regulatory law.  In 2004, Heather was awarded a Pegasus scholarship to work in Virginia, USA; she also worked at the European Commission in Brussels for several months in 2008. She joined Chambers in 2009.

Professional Memberships

  • Professional Negligence Bar Association (Executive Committee, 2020 to present)
  • London Common Law & Commercial Bar Association

Publications

Heather assisted with research for Flenley and Leech, The Law of Solicitors’ Liabilities, fourth edition, 2020. Her own published work includes “Loss of a chance in commercial transactions”, Butterworths Journal of International Banking and Financial Law, 2021, 405 (with Michael Pooles KC).

Personal

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. 

Heather McMahon is a barrister regulated by the Bar Standards Board. Click here to view Heather McMahon’s Privacy Notice