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Oliver Assersohn

Oliver Assersohn

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Oliver Assersohn is a commercial and regulatory barrister specialising in banking and financial services and is recommended by the foremost independent legal directories including by Chambers & Partners 2016 in Band 1 (non-QC’s) for financial services. Chambers & Partners write: “A financial services and banking specialist who has a wealth of expertise in the area. He has a broad chancery and commercial practice…He is incredibly diligent and hard-working, and continues to impress with his technical knowledge.”

The majority of Oliver’s commercial work has a banking or financial services angle to it and he has acted for institutions, funds, family offices and individuals. In addition to an analysis of the contractual, equitable and common-law position Oliver is able to bring to bear his detailed knowledge of the Financial Services and Markets Act (2000), the regulatory regime more generally and the impact of the FCA rules on a civil claim. Oliver also has undertaken a number of non-financial services related commercial cases for negligence, breach of contract as well as being instructed in interlocutory applications and jurisdictional issues with particular experience of forum non conveniens applications.

As to his regulatory work, examples of previous quotes from clients that have been included in the directory are: “Understands how the regulator lives and breathes” and “Very bright, exceptionally hardworking, personable and very practical. He really understands the FCA’s enforcement process.” Oliver was previously seconded to the Regulatory Decisions Committee of the FSA (which decides contested enforcement decisions) and advised the FSA in a number of cases as well as having been instructed by the enforcement division (so far as he knows he is one of only two barristers in private practice to have been embedded in the RDC in this way). Oliver has acted for individuals and institutions subject to investigation by the FCA. He has extensive experience of market abuse and insider dealing issues (for example he acted for the FSA as junior counsel in the first FSA initiated prosecution for insider trading (both defendants were convicted) and subsequently acted as junior counsel for one of the defendants in the first FSA initiated prosecution for insider trading to end in acquittals). He is the editor of the Decision Procedure and Penalties Manual Commentary in Butterworths Financial Regulation Service.

Some sample cases are cited under the relevant tabs below.

Oliver is regularly requested to give talks to leading law firms and has written on a number of financial services and legal issues (see “Publications” below).


  • Published a variety of articles in numerous publications on financial services and banking matters and gave talks on current issues to solicitors and clients.
  • Editor of the Decision Procedure and Penalties Manual Commentary in Butterworths Financial Regulation Service (c. 40,000 words) (published March 2015).

Commercial & Chancery

X v Brokerage House (2016, settled after pleadings and mediation)

Recently acted for claimant in High Court claim alleging breach of contract, negligence and the FCA rules in relation to the brokerage house’s decision to (among other things) follow the instructions of a person to whom the claimant had granted third party authority and which resulted in the loss of almost the entire sum invested.

Y v Z (2015)

Claim by major financial institution against another in respect of unpaid commission payments which the defendant refused to pay on the basis that to do so would breach the FCA Rules (they had not been disclosed by the defendant to its customers).

Mengiste & Anor v Endowment Fund for the Rehabilitation of Tigray & Ors [2014] EWHC 4196 (Ch)

Following the decision referred to above and the claimant’s subsequent application in Ethiopia, represented the defendants as sole counsel in successfully resisting the claimants’ application to lift the stay in this US$20m claim. The claimants currently have permission to appeal following an oral hearing before the Court of Appeal on condition they pay the defendants £200,000 in costs.

Mengiste & Anr v EFFORT & Ors [2013] EWHC 1718

Acted for the defendants who were being sued for $20m by the claimants who allege that the defendants obtained a judgment in Ethiopia by fraud. The defendants applied to stay the claim on the grounds of forum non-conveniens and the central issue has been whether or not there is cogent evidence that the claimants will not receive justice in Ethiopia. The claim was stayed on grounds of forum non-conveniens pending the Claimants being allowed time to make an application in Ethiopia. The case involved a range of subsidiary issues, most notably whether an expert witness in fear of his life could remain anonymous ([2012] EWHC 2782 (Ch)). Other reported decisions as part of the EFFORT litigation included: [2013] EWHC 598 (Ch) (22 March 2013); [2013] EWHC 856 (Ch) (25 March 2013); EWHC 857 (Ch) (26 March 2013); EWHC 1087 (Ch) (1 May 2013); EWHC 1003 (Ch) (14 August 2014).

EFFORT & Ors v Rylatt Chubb [2013] EWHC 1003

Acted for EFFORT in an application for wasted costs against the claimants’ solicitors relating to their choice of expert for the underlying action. The matter was appealed to the Court of Appeal.

The Great Estates Group Limited v Digby [2011] EWCA Civ 1120, [2011] 43 EG 104(CS)

Acted for the vendor of a private home who was sued by an estate agent who claimed that he was instructed as a sole agent and that he was entitled to damages for loss of the chance of earning commission when the sale of the property was not arranged through him. Successfully argued at first instance that the contract could not be enforced because the agreement did not comply with the Estate Agents Act (1979). The claimant appealed to the Court of Appeal, who by a majority (Lord Justice Lloyd dissenting) upheld the first instance decision. One of several estate agency cases undertaken.


A lender v X (2016)

Acted for a lender bringing proceedings against a borrower in relation to a £4m mortgage. The borrower was seeking to avoid liability by (among other things) arguing that the loan was made in breach of the Financial Services and Markets Act (2000) and is therefore unenforceable. Settled during opening speeches.

Interest rate swap mis-selling claims (ongoing)

Acted in a large number of interest rate swap mis-selling claims against banks. Represented individuals and companies in pursuing compensation through the courts and advising on aspects of the FCA ordered redress scheme. In addition to the familiar contractual, common-law and statutory causes of action he has been involved in cases alleging negligence in relation to the implementation of the FCA Redress Scheme.

Y Ltd v A Bank (2016)

Acted for a company seeking to bring Holmcroft style judicial review proceedings of the actions of an independent reviewer.

Z and the LIBOR investigation (ongoing)

Instructed on behalf of a party that has been investigated in relation to the investigation into the manipulation of LIBOR in the context of potential civil claims.

Financial Services

Regulatory cases (for civil claims please see “banking ” and “commercial and chancery ” tabs):


Acted for brokerage subject to FCA enforcement action.


Acting for individual subject to FCA enforcement investigation.


Recently acted for individual applying to lift a prohibition order on an individual.

Z v A Bank

Advising compliance officer of a major global financial institution in respect of her whistleblowing and subseqient disciplinary proceedings in context of wider regulatory investigation.

After secondment to the Regulatory Decisions Committee of the FSA, continued to advise the Committee in a variety of cases. For example, he advised the Committee in FSA v (1) Visser (2) Fagbulu in which a ban and £2.1m fine were imposed on a hedge fund chief executive and chief financial officer for deceiving investors and market abuse.

Appointments & Memberships

  • FSLA (Founding Member)


  • Queen Mother Fund Scholarship (2002)
  • Blackstone Entrance Exhibition (2002)
  • Queen Mother Fund Scholarship (2001)

Areas of Law




“An effective advocate. Knowledgeable, punchy and not overly aggressive.” Financial Services, Chambers & Partners 2018

“Very good for fraud and financial regulatory investigations.” Financial Services, Legal 500 2017

“He is instructed on complex financial services-related matters.” Business and Regulatory Crime, Legal 500 2017

“Highly rated for banking and financial services disputes.” Banking and Finance, Legal 500 2017

“His written work is always excellent, he provides clear and practical advice and he deals with clients in a very empathetic manner.” Financial Services, Chambers & Partners 2017

“Technically bright, hardworking, a team player and approachable.” Business and Regulatory Crime, Legal 500 2016 

“A truly excellent barrister, who knows the ins and outs of FCA regulations.” Banking and Finance, Legal 500 2016

“A financial services and banking specialist who has a wealth of expertise in the area. He has a broad chancery and commercial practice…He is incredibly diligent and hard-working, and continues to impress with his technical knowledge.” Chambers & Partners 2016

“He has a very innate feel for the regulators’ expectations and is very good at the detail. He understands the issues and is very diligent and analytical.” Chambers & Partners 2016

“Very bright, exceptionally hardworking, personable and very practical. He really understands the FCA’s enforcement process.” Chambers & Partners 2015

“He is calm, knowledgeable, diligent and keen to assist. A pleasure to work with.” Chambers & Partners 2015

“Extremely well regarded for financial services and FCA regulatory issues.” Legal 500 2015

“The barrister to go to with challenging issues.” Legal 500 2015

“An absolute delight to work with.” Chambers & Partners 2014

“Highly experienced in regulatory and FCA related matters.” Legal 500 2014

“A financial services specialist.” Legal 500 2014

“First rate.” Chambers & Partners 2013

“An enviable reputation as a leading junior in financial services law.” Chambers & Partners 2012

“The ‘knowledgeable, calm and authoritative’ Oliver Assersohn is recommended for contentious financial services work, where ‘his experience is almost unique’.” Legal 500 2012

“Highly diligent.” Chambers & Partners 2011

“Invaluable knowledge of the FSA disciplinary process.” Legal 500 2011

“Understands how the regulator lives and breathes.” Chambers & Partners 2010

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