Thomas Mason

Thomas is instructed by both paying and receiving parties in all areas of costs and litigation funding.

His practice focuses on the following areas:

• Commercial litigation – Instructed by solicitors from a roster of leading national and international law firms in multi-million pound detailed assessment proceedings related to high value, high-profile and complex cases in the Commercial Court.
• Solicitor/client advisory –Having been a Partner in a firm of solicitors, Thomas has valuable insight into the working practices of solicitors. He has used this knowledge to draft retainer documentation and provide advice to a number of law firms on effective compliance with statutory, common law and regulatory requirements.
• Solicitor/client litigation – Acting for firms of solicitors to robustly defend challenges to their fees and also acting for companies/high net worth individuals to bring challenges to solicitors fees at detailed assessment. This work often includes complex legal and factual disputes on retainer documentation and the status of interim statute bills.
• Medical negligence, professional negligence and personal injury – Instructed on a full spectrum of cases from fixed costs test cases to detailed assessments in high value, complex and difficult cases.

Thomas’ commercial work generally focuses on disputes between solicitors and their former clients:

• Thomas is regularly instructed by solicitors to recover their unpaid fees from former clients. Thomas is also regularly instructed by former clients seeking to defend proceedings brought by their former solicitors. This work involves an international element including work in Singapore and Abu Dhabi.
• Thomas is also often instructed by solicitors to obtain urgent interim remedies to preserve funds where there is a risk of dissipation by the former client, including injunctions and orders pursuant to s73 of The Solicitors Act 1974.

Recent work includes:

• Topalsson GmbH v CMS Cameron McKenna Nabarro Olswang LLP [2025] EWHC 118 (SCCO). A 4 day trial on the status of interim statute bills and wrongful termination in a multi-million pound dispute between Topalson GmbH and their former solicitors (instructed by the successful Claimant unled against Alexander Hutton KC).
• Attersley v UK Insurance Ltd [2025] EWHC 884 (KB). Led by Alexander Hutton KC, instructed by the successful Appellant. Stacey J concluded that a Claimant is entitled assessed costs in circumstances where a claim has been submitted via the RTA Protocol, a Part 36 offer is made prior to allocation but not accepted until the relevant period has expired following allocation to the multi-track.
• Franklin v Your Lawyers Ltd [2025] EWHC 984 (SCCO). A decision of Senior Costs Judge Rowley on s68 of the Solicitors Act 1974.
• Gorenstein v Sears Tooth Solicitors [2025] EWHC 1114 (SCCO). A decision of Costs Judge Nagalingam on s74(3) of the Solicitors Act 1974.
• Challis v Bradpiece [2024] EWHC 1124. A decision of Deputy Costs Judge Roy KC which determined that QOCS applied to detailed assessment proceedings.
• Camran Mirza & Ors v CMS Cameron McKenna Nabarro Olswang LLP [2024] EWHC 2058 (Ch). A decision of Master Kaye in relation to a declaration sought that monies paid were held on trust only for the purpose of paying counsel’s fees (appearing unled against Roger Mallalieu KC).
• Acting for the receiving party in multi-million pound detailed assessment proceedings related to a billion-dollar fraud dispute in the Commercial Court. The case involved a novel preliminary issue on the format of precedent S.
• Acting in multi-million pound detailed assessment proceedings following a billion dollar, multi-party Commercial Court dispute. The case involved complex division between multiple parties with issue-based costs orders.
• Acting for the paying party in multi-million pound detailed assessment proceedings against its former solicitors. The underlying litigation was a billion-dollar dispute with a nation state. The case involved jurisdictional issues, complex factual evidence, alleged wrongful termination of a retainer and the status of interim statute bills.
• Acting for the receiving party in multi-million-pound detailed assessment proceedings. The case involved novel issues on the definitions in a funding arrangement, the presentation of certain categories of costs in precedent S and the operation of Part 36.
• Advising a new law firm on appropriate funding models and ATE/medical agency commissions. The advice involved work with innovative technology and novel ways to meet statutory and common law requirements.

Recommended as a Rising Star for the London Bar Legal 500 2025:

“Thomas is meticulous in his preparation for any advice or hearing. He has an impressive understanding of legal costs authorities and is a formidable advocate.”

Recommended as Up and Coming in Chambers and Partners UK Bar Guide 2025:

“I was very impressed with Tom Mason. He’s an up and coming junior above his year of call, who’s got a good deal of experience.”

“I know Thomas and I like that he has 'lived' experience as a cradle-to-grave drafter - this makes him an attractive costs counsel to instruct.”

Thomas is passionate about social mobility, access to justice and education.

His work in these areas includes:

• An advocacy tutor on the Association of Costs Lawyers advocacy course.
• A mentor at the Social Mobility Foundation helping high-achieving young people from low-income backgrounds succeed at top universities and in professional careers.
• The co-founder of a legal tech start up whose aim was to help litigants in person navigate the small claims procedure.

ICO Data protection registration number: ZB539693

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