"William is the best professional negligence barrister in the UK. His approach (beyond meticulous) and manner (friendly and affable whilst brutally honest when needed) are both perfect for the kind of work we do" (Chambers Directory 2024).
“He is the pre-eminent professional negligence lawyer and is very approachable and technically adept. Clients love him too.” (The Legal 500 2023.)
William Flenley KC specialises in all aspects of professional liability, and related insurance issues. His recent cases in the law reports include appearing
William is also instructed as an arbitrator, mediator and adjudicator, and worked on the design of the Professional Negligence Bar Association’s adjudication scheme.
He is the co-author, with Mr Justice Leech, of the leading text on claims against solicitors, The Law of Solicitors’ Liabilities, first published in 1999 and now in its fourth edition. He is a former Chair of the Professional Negligence Bar Association, has contributed to Professional Negligence and Liability and Cordery on Legal Services, and was deputy editor of Lloyd’s Reports: Professional Negligence. He is a Bencher of the Middle Temple, and Vice-Chair of its Estates Committee. He has been recommended for professional negligence in Chambers’ Directory for 24 years, and is a popular speaker on professional liability topics.
William is a former board member of homelessness charities Bondway and Thames Reach Housing Associations.
Accountants & auditors
William acts in complex and large-scale claims against auditors and accountants. This includes advising in the defence of a £20m claim against auditors for alleged failure to report fraud, and a £5m claim against auditors in relation to the sale of a national chain of retailers.
Insurance brokers
William’s work involving insurance brokers includes acting in claims relating to alleged failures concerning business interruption cover, and failures to give proper advice concerning a burglar alarm warranty. In this area, William additionally benefits from his substantial experience of dealing with insurance coverage disputes between insured and insurer.
Financial professionals
William is active in this area of work and has acted for financial advisors in a 14-party claim under the Financial Services and Markets Act and at common law, listed for a 4 week trial before it settled, and a £500,000 claim against financial advisors in relation to their alleged promotion of an investment bond which failed.
Lawyers
William is co-author of the leading text Flenley & Leech, Solicitors’ Negligence & Liability, now in its third edition. He regularly advises and appears in high value and complex claims against lawyers. Recent cases include Group Seven and Giambrone, both mentioned at the start of this c.v.
Surveyors & valuers
William is very familiar with claims against surveyors and valuers, including mortgage lenders’ and contribution claims. He wrote the discussion of SAAMCo in Professional Negligence and Liability (ed.Simpson). In Nationwide BS v Dunlop Haywards [2010] 1 WLR 258, a lenders’ claim, he obtained an order that fraudulent surveyors pay contribution of £4.5m. He also acts in claims by purchasers against surveyors, and recently represented surveyors in a complex case as to whether purchasers should give credit for improvements to their property after the date of the surveyors’ negligence.
William is a trained mediator and, at the invitation of the parties, recently gave early neutral evaluation of a claim’s merits. He also appears as a mediation advocate, advising on whether and when to mediate and preparation for mediation, settling mediation statements and appearing at mediations.
William regularly deals with a variety of issues relating to insurance coverage, particularly in connection with professionals, often appearing at arbitrations, as well as acting as an arbitrator in this context. Recent work has involved a £10m coverage dispute in relation to insurance of wind farms, which settled, and successfully showing lack of cover under the Solicitors’ Minimum Terms in relation to over 50 claims.
William appears at arbitrations and as an arbitrator (see the last heading), and has been involved in the launch of an Adjudication scheme for professional liability cases. He has acted as an adjudicator under that scheme, having previously undertaken a short course in Adjudication at University College, London.
"William is a go-to counsel on solicitors' cases." Chambers UK, 2025
"William is very impressive, quick to respond, user-friendly and very intellectually imaginative." Chambers UK, 2025
"William is a fantastic silk and a leader in his field. Not only is he excellent with clients but he's extremely user-friendly and will maintain a strategic focus throughout." Chambers UK, 2025
"William has an encyclopedic knowledge of the law and is an excellent advocate in court." Legal 500, 2025
"William is the best professional negligence barrister in the UK. His approach (beyond meticulous) and manner (friendly and affable whilst brutally honest when needed) are both perfect for the kind of work we do." Chambers UK, 2024
"William is an expert in this field. He is incredibly intelligent, hard-working and technically adept but he is also prepared to think outside the box." Chambers UK, 2024
"William is very approachable and has an excellent way with clients." Chambers UK, 2024
"William gets straight to the heart of the matter. Makes the complex simple." Chambers UK, 2024"
Clear, considered, detailed and well structured advice, both written and in conference. Understanding and considerate of views of clients. Always fabulously well prepared. Respectful and never too busy to discuss." Legal 500, 2024
"William is unrivalled in his attention to detail; there is absolutely no way that William would ever take a matter to trial that he does not know inside out and backwards. You just know that everything will be done right." Chambers UK, 2023
"He is is the pre-eminent professional negligence lawyer and is very approachable and technically adept. Clients love him too." Legal 500, 2023
“He’s a very cerebral barrister and fantastic to work with.” “He’s fantastic, the perfect foil to difficult clients. You can be confident that he’s looking unemotionally at the issues, not getting distracted by the heat and noise.” “Quite simply the best in my opinion. He’s excellent, not only extremely bright but user-friendly and really good with clients, and responsive. He lives up to his reputation.” Chambers UK, 2022
"Very willing to listen to the ideas of others and assimilate them as necessary. Very experienced indeed in solicitor negligence and insurance coverage. Gives extremely clear advice. Very good on tactics and thinking through the consequences of strategic decisions." Legal 500, 2021
“His knowledge and ability to get to grips with the evidence is impressive.” Chambers UK, 2021
“A top KC because he is incredibly intelligent and hard working.” Chambers UK, 2021
“His technical attention to detail is fantastic and we are confident that he’ll sort through everything carefully and properly.” Chambers UK, 2020
“An outstandingly good performer in his field.” Chambers UK, 2020
“When it comes to professional liability, there can be few at the Bar who are as knowledgeable and as skilled as he is” Legal 500, 2020
“He is outstanding technically, and just completely straightforward and transparent – no pomposity or flannel. I know he gives me the right advice, without any attached motive” Chambers UK, 2019
“An impressive advocate with some fearsome intellect. He instantly gets to the nub of the issues and comes up with novel arguments to blow the other side’s case out of the water” Chambers UK, 2019
“He is fabulously persuasive in court and his advice is clear, concise and utterly reliable” Legal 500, 2019
“He has phenomenal knowledge and an amazing mind. Judges really listen to him. He’s a great talent” “Extremely knowledgeable in dealing with complex solicitors’ claims” Chambers UK, 2018
“He is approachable and user-friendly, and has the gravitas required to intimidate the opponent” Legal 500, 2017
“William Flenley is concise, and incredible likeable as well.” Chambers UK, 2017
“Technically very strong” Legal 500, 2016
Chambers UK, 2016 said that he “has a wealth of experience acting in all kinds of major negligence claims, including those brought against barristers, financial advisers and insurance brokers. Frequently instructed to act in the most sophisticated matters at the cutting edge of the field.”
“Extremely tenacious and thorough”. Legal 500, 2015
“an eye for detail and is very good at thinking outside the box.” "He is very clever, meticulous in his approach and an excellent cross-examiner.” Chambers UK, 2015
“excellent analytical skills.” Legal 500 2014
“a real favourite of large insurers, and a lawyer with particular expertise on solicitors’ negligence cases. ‘Meets deadlines, gives clear advice and is also exceedingly nice’. ‘He’s a quick-witted advocate’.” Chambers UK, 2014
Axis v Discovery Land [2024] PNLR 16 – solicitors’ professional indemnity insurance, meaning of ‘to condone’, aggregation.
King v Stiefel [2023] PNLR 18 – the test for stage 1 of a wasted costs application in the context of complex Commercial Court litigation.
Discovery Land v Axis [2021] Costs LR 777. Costs budgeting in the Commercial Court.
Addlesee v Dentons Europe [2020] Ch 243, Court of Appeal authority on what happens to the legal professional privilege of a company after it has been dissolved.
Group Seven v Notable Services [2020] Ch 129, the most recent Court of Appeal authority on the mental element of dishonest assistance in breach of trust.
Various Claimants v Giambrone [2018] PNLR 2, breach of trust and the application of BPE and Saamco to claims against lawyers.
Purrunsing v A’Court [2016] 4 WLR 81, (Ch Div), identity fraud, liability of lawyers acting for buyer, and for seller. Widely discussed in the legal press.
Harding Homes v BDB [2015] EWHC 3329 (Ch), successfully proved that solicitors who admitted negligence re banking security documents had caused no loss.
Edwin Coe v Aidiniantz [2015] 1 Costs L0 129, assessment of solicitor’s costs, s.70 Solicitors Act 1974.
Credit & Mercantile v Nabarro [2015] PNLR 14 (Ch Div), achieved summary judgment for the defendant in limiting damages for professional negligence to diminution in value.
Nationwide BS v Davisons [2013] PNLR 12. Court of Appeal authority on claims against solicitors for breach of trust and allegations of breach of strict contractual duty.
St Anselm v Slaughter & May [2013] EWHC 125 (Ch), acting for the defendant, struck out half of claim on limitation grounds.
Hellard v Irwin Mitchell [2013] PNLR 8 implied waiver of privilege as to evidence of barristers.
Nationwide BS v Dunlop Haywards [2010] 1 WLR 258, [2009]. An important decision on contribution between valuers and solicitors in lenders’ claims.
Pickthall v Hill Dickinson LLP [2009] EWCA Civ 643, and [2009] PNLR 10. Limitation and abuse of process.
Taylor Walton v Laing, [2008] PNLR 11. Solicitors’ negligence, successful strike out of relitigation as abuse of process (also the subject of a feature article in The Times).
Stone Heritage v Davis Blank Furniss, [2007] EWCA Civ 765, [2007] 31 EG 80 (CS): successful appeal on scope of solicitor’s duty to give commercial advice.
Luke -v- Wansbroughs [2005] PNLR 2, QBD: duty of barristers and solicitors in the conduct of litigation.
Luke -v- Kingsley Smith & Co [2004] PNLR 12, QBD: test in law as to when solicitors and barristers may seek contribution from each other.
Laib -v- Aravindan [2003] EWHC 2521, QBD, The Times, 13 November 2003: claim for loss of litigation, accrual of cause of action.
Direct Line Insurance v Khan [2002] Lloyd’s Rep IR 364, CA: insurance; joint policy; whether fraud of one policyholder entitled insurers to recover sums paid to both policyholders.
Ruparel v Awan [2001] Lloyd’s Rep PN 258, Ch D. Enforcement of solicitors’ undertakings and the Partnership Act; whether work done in the ordinary course of solicitor’s business.
Jenmain Builders v Steed & Steed [2000] PNLR 616,CA. Measure of damages for professional negligence, whether loss of profits recoverable.
Matlock Green Garage Ltd v Potter Brooke-Taylor & Wildgoose [2000] Lloyd’s Rep PN 935, QBD: measure of damage for solicitors’ negligence leading to loss of business tenancy; valuation of tenancy.
Nationwide BS v Balmer Radmore [1999] Lloyd’s Rep PN 241, [1999] PNLR 606, Ch D. Managed list of 400 cases relating to solicitors’ liability to mortgage lenders, contributory negligence in solicitors’ cases, breach of fiduciary duty, relevance of surveyors’ negligence. Specifically, William acted as junior counsel in:
Bristol & West Building Society v. Daniels & Co [1997] PNLR 323,Ch D. Solicitors’ negligence/breach of fiduciary duty.
Melinek & Back [1997] BPIR 358, The Times 10 April 1997, ChD. Solicitors’ negligence, insolvency law.
Mahoney v. Purnell [1996] 3 All ER 6 QBD. Solicitors’ negligence, accountants’ negligence, undue influence.
R v. Poole BC, ex parte Cooper 27 HLR 605, Crown Office List. Judicial review, homelessness.
Irtelli v. Squatriti [1993] QB 83, CA. Contempt of court.
Publications
Co-author, Solicitors’ Negligence and Liability (Flenley & Leech, 3rd ed., 2013).
An original contributor to Professional Negligence and Liability (Informa): sections on SAAMCo, causation, mitigation, contribution.
A former contributor to Cordery on Legal Services.
Formerly assistant general editor, Lloyd’s Reports: Professional Negligence (2000-2003).
Ough and Flenley, The Mareva Injunction and Anton Piller Order (2nd ed., 1993): freezing orders, search and seizure orders.
He has also spoken at professional negligence events organised by CLT, Informa, Lexis Nexis, the insurers’ Professional Indemnity Forum, the Professional Negligence Law Association, and the Professional Negligence Bar Association (PNBA), including webinars. From 2007 until 2010, he was co-chair of the annual PNBA Lawyers’ Liability Day.
Education
MA (Oxon) (Jurisprudence) (1985), Open Exhibition
LL M (Cornell Law School, USA), St Andrew’s Society of the State of New York Scholar (1986)
BCL (Oxon) (1987), Middle Temple Astbury scholarship (1988)
Mediation training (ADR Chambers)
Appointments
Part-time lecturer in Law, London School of Economics, 1988-89
Bencher of the Middle Temple, 2014
Committees
Executive Committee, Professional Negligence Bar Association, 2004-2015; Vice-Chairman 2011 to 2013; Chairman 2013 to 2015.
Since 2015, he has sat on a committee seeking to introduce a scheme of Adjudication to Professional Liability cases.
Member, Board of Management, Thames Reach Housing Association, a charity for people who are homeless or in danger of homelessness in London.
ICO Data protection registration number: Z6874737.
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