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. 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.

Recent work includes:

• 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.
• An application for a payment on account of costs and forthwith order for detailed assessment relating to a multi-million pound claim against the underwriters of an insurance policy.

"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." Chambers UK, 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." Chambers UK, 2025

“fantastic” Legal 500, 2023*

“very responsive, commercially minded and has a great demeanour for putting clients at ease” Legal 500, 2023*

*as a solicitor

Thomas is passionate about social mobility and access to justice.

His work in these areas includes:

• 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.

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