"He's completely dedicated to his clients, has very good judgement and is always looking for a pragmatic way through." "He is a really good practitioner and strategist."
Chambers UK 2021


Will Glassey is head of Insurance in London. He is a litigator, whose primary practice area is representing professional firms and individual professionals in professional negligence claims. He has a particular emphasis on defending claims against solicitors, barristers, pensions actuaries and property professionals. For this work he is ranked in Band 1 by the legal directories including Chambers

The subject matter of the claims he defends is diverse, but he has a particular focus on claims arising from transactions, including corporate, commercial, real estate and finance transactions, and he has extensive experience in claims arising from pensions and tax issues.

In addition, Will represents professional firms and individual professionals in regulatory investigations and disciplinary proceedings: he has handled matters before the Solicitors Regulation Authority, the Solicitors Disciplinary Tribunal, the ICAEW, the Serious Fraud Office, the Royal Institution of Chartered Surveyors, the FCA, and the Takeover Panel.

He also advises insurers on policy coverage issues arising in claims against professionals, and represents insurers and reinsurers in reinsurance coverage disputes.

Will joined Mayer Brown in 2000 and was made a partner in 2002. Previously, he worked with one other major UK law firm, after qualifying as a barrister and solicitor (1994) with an Auckland, New Zealand firm.

Spoken Languages

  • English


  • Raffeisen Bank International AG v Asia Coal Energy Ventures Ltd & Ashurst LLP [2020] EWCA Civ 11: successful defence at trial of a substantial claim against a firm of solicitors relating to a letter written by the firm in the course of a corporate/ finance transaction. 
  • Civil Aviation Authority v Jet2.Com Ltd [2020] EWCA Civ 35: representing the CAA in an important decision concerning the scope of Legal Advice Privilege including particularly the application of the ‘dominant purpose’ test to multi-addressee email communications.
  • Briggs v Clay [2019] EWHC 102 (Ch): representing the parties applying successfully to strike out references to Without Prejudice communications from a pleading; the Court considering the scope of the ‘Muller v Linsley & Mortimer’ exception to Without Prejudice privilege.
  • Raiffeisen Bank International AG v Asia Coal Energy Ventures Ltd & Anor [2019] EWHC 3 (Comm): Successful defence of a specific disclosure application against Mayer Brown’s law firm client in relation to a corporate transaction, the applicant having sought disclosure of documents subject to legal advice privilege.
  • Libyan Investment Authority & Ors v Warwick Street (KS) LLP & Ors [2018] EWHC 2952 (Ch): Successful striking out of a deceit claim against Mayer Brown’s real estate consultancy client, the claim relating to the claimant’s investment in a hotel and retail development project.
  • Rehman v Santander UK Plc [2018] EWHC 748 (QB): Successful summary judgment application in respect of a professional negligence claim against Mayer Brown’s real estate consultancy client, the claim being dismissed for the absence of any duty owed by our client to the claimants.
  • Impact Funding Solutions Limited v Barrington Support Services Limited v AIG Europe Limited [2015] EWCA Civ 31. UK Court of Appeal decision concerning coverage under a solicitors’ professional liability policy for debts incurred by a law firm to litigation funders. Permission has now been given for appeal to the Supreme Court, which will be heard in March 2016. The Supreme Court is being asked to consider what liabilities are integral parts of a solicitor’s practice and thus covered by professional indemnity insurance; and which liabilities are excluded as being a trade debts.
  • AIG Europe Ltd v The International Law Partnership (OC320301 LLP) & others [2015] EWHC 2398. Representing insurers, in a dispute with claimants against a dissolved law firm, about the application of the Minimum Terms aggregation clause, to determine how many policy limits are exposed. The claimants succeeded at first instance in the Commercial Court and permission has been given to appeal to the Court of Appeal.
  • Freemont (Denbigh) Limited v Knight Frank LLP [2014] EWHC 3347 Successful defence of a professional negligence claim against a firm of property valuers, following a Chancery Division trial. The claim concerned the valuation of a substantial development site in North Wales. Unusually, the claim was brought by the borrower, not by the firm’s lender client.
  • Starlight Shipping Co v Allianz Marine & Ors (‘The Alexandros T’) [2014] EWCA 1010 English Court of Appeal decision concerning the finality of a settlement agreement, in the context of a claim being brought against our English law firm client in Greece.
  • S & T v L [2014] EWHC 5 (Admin) Appeal in solicitors’ disciplinary case (arising from allegations of misleading the Court in an injunction application), from the Solicitors Disciplinary Tribunal to the Administrative Court.
  • Impact Funding Solutions Limited v Barrington Support Services Limited v AIG Europe Limited (AIG) [2013] EWHC 4005 (QB) Successful trial of solicitors’ policy coverage issues (currently subject to appeal).
  • Dorchester Project Management Ltd v BNP Paribas Real Estate Advisory & Property Management UK Ltd (2013) Court of Appeal determination of preliminary (construction) issues in a dispute concerning a Non-Disclosure and Non-Circumvention Agreement entered into by our professional firm client.
  • Starlight Shipping Co v Allianz Marine & Ors (‘The Alexandros T’) Supreme Court [2013] UKSC 70; Court of Appeal [2012] EWCA Civ 1714; Commercial Court: [2011] EWHC 3381 (Comm) Landmark Supreme Court decision in our clients’ favour, in the context of a claim against English solicitors brought in Greece, concerning the lis alibi pendens provisions (Articles 27 and 28) of the Brussels Regulation.
  • Jenkins v Royds (25666/2012 Supreme Court: Queen’s County, State of New York). Together with New York colleagues, successful motion to dismiss claim against English solicitors in New York, for want of personal jurisdiction.
  • Sutherland Professional Funding Limited v Bakewells (Third Party Chartis Insurance (UK) Limited) [2011] EWHC 2658 (QB): Successful representation of insurer in coverage dispute concerning scope of cover under solicitors’ policy. It was held that there was no cover for contractual guarantees given by a law firm to a third party litigation funder.
  • Tamlura NV v CMS Cameron McKenna [2009] EWHC 538 (Ch): Successful defence at High Court trial of a professional negligence claim against solicitors arising from sale of a private company to a listed company. The allegations concerned the valuation mechanism for deferred consideration shares.
  • Fulham Leisure Holdings Limited v. Nicholson Graham & Jones [2006] EWHC 2017 (Ch): Successful defence at High Court trial, then in the Court of Appeal and, at the permission stage, in the House of Lords, of a professional negligence claim against solicitors arising from a corporate acquisition: Mohamed Al Fayed’s acquisition of Fulham Football Club. The allegations concerned the provisions in a Shareholders' Agreement for the basis upon which the acquiring, majority shareholder would invest in the Club.
  • Cumbria Waste Management Ltd v Baines Wilson (A Firm) ([2008] ADJ.L.R. 04/16): in the context of the defence of a professional negligence claim against a firm of solicitors, an important decision about whether documents from a previous mediation are able to be disclosed in subsequent proceedings.
  • Eagle Star v Cresswell ([2004] All ER (Comm) 244): Trial of legal issues in a reinsurance coverage dispute: whether a claims co-operation clause in a facultative reinsurance contract had the effect of a condition precedent. Successful on appeal to the Court of Appeal in establishing that the clause did have the effect of a condition precedent to cover.
  • 2004 – 2007: Resolution of numerous liability claims against Momart Limited, the fine art packers and shippers, arising from a catastrophic fire at its fine art storage facility on 24 May 2004. Issues included bailee's liabilities, application and incorporation of Standard Trading Conditions including limitation of liability, and forensic fire investigation.


University of Auckland, LLB (Hons)


  • England and Wales
  • New Zealand

Consistently recommended and ranked as a key individual by the legal directories:

  • Listed as a 'Leading individual' for professional negligence and a 'key name for contentious pensions matters'. He '...excellent at dealing with complex legal and policy issues.’ (Insurance & Reinsurance litigation). (Legal 500 2021). 
  • William Glassey's expertise covers breach of contract and liability claims, with a particular focus on defending international firms and barristers, as well as their insurers. "He's completely dedicated to his clients, has very good judgement and is always looking for a pragmatic way through." "He is a really good practitioner and strategist." (Chambers UK 2021).
  • Listed as a 'Leading Individual', William Glassey is distinguished in the field for his work on solicitor's negligence claims. "He's clever and on the ball," notes an interviewee. (Chambers UK 2020).
  • Listed as a 'Leading Individual' 'Practice head William Glassey has particular expertise in professional indemnity' (Legal 500 2020);
  • The "excellent" William Glassey assists with negligence matters relating to a range of professionals, maintaining a particular focus on work for those in the legal and financial services sectors. Market commentators describe him as "unflappable and very commercial." (Legal 500 2019 Professional Negligence);
  • The "unflappable and very commercial" William Glassey is a "rare mix of technical legal knowledge, gravitas and practicality". (Legal 500 2018 Professional Negligence);
  •  The "outstanding" William Glassey "commands respect both from his own clients and opponents" as a result of the "careful preparation and superb judgement he brings to any case". (Legal 500 2018 Financial Services);
  • William Glassey "is always a good man to have on your side. He's very knowledgeable and client-friendly but also a powerful advocate; he won't be bullied." His recent work has seen him advise insurers and construction professionals as well as barristers and solicitors. (Chambers UK 2018);
  • The "astute and authoritative" William Glassey is "unrivalled in intellectual firepower" and jointly heads the practice. (Legal 500 - Professional Negligence, 2017) 
  • The "pre-eminent" William Glassey devotes a large proportion of his work to professional negligence claims, acting for major law firms and their insurers. He combines a focus on claims that relate to commercial and financial transactions with advice on claims from general pension and tax matters. (Chambers UK 2017);
  • "Truly brilliant" (Legal 500 2016); 
  • Joint head of department William Glassey is admired by clients for his technical prowess and for bringing a commercial perspective to cases. Sources say he "really gets on top of the detail, is an able tactician and is absolutely loved by all his clients." He has extensive experience in financial and property-related professional negligence claims. (Chambers UK 2016);
  • Chambers UK 2016 ranks 30 Mayer Brown practices and 47 lawyers.
  • "Truly brilliant" (Legal 500 2015);
  • The "exceptional" William Glassey is praised by market sources as "very commercially minded, articulate, persuasive and rational." He is highly regarded for complex legal professional negligence cases. Clients note: "He has a calm and methodical approach but can be forceful when he needs to be - an extremely good advocate to have on your side." (Chambers UK 2015);
  • "top notch" (Legal 500 2014);
  • William Glassey is extremely well regarded by peers who mention him as a go-to person for the largest, most complex claims. Well known for defending lawyers, he "exudes authority and keeps very level-headed." (Chambers 2014);
  • William Glassey has "an extraordinary appetite for hard work", and "invaluable breadth of experience" (Legal 500 2013);
  • the "terrific" William Glassey has an all-round ability that "commands the respect of the market." (Chambers UK 2013);
  • "First-class" he is deemed someone whose "star is in the ascendant" He gains praise for his "direct approach" and a "razor-sharp mind that cuts through the issues" (Chambers UK 2012);
  • He is "proactive" (Legal 500 2012);
  • He "continues to excel" with "novel and compelling approaches to complex matters" (Legal 500 2011);
  • He "has a real skill in striking up good relationships with accused professionals; he really holds their hand and gets the best out of a case as a result" (Chambers UK 2011);
  • He is praised for his "terrific defence of barristers who find themselves in hot water" and it is said that he is "an absolute joy to work with". (Chambers UK 2010);
  • Simply "excellent" he is a "very tenancious, effective litigator" (Legal 500 2010).