About Mithril

Built by entrepreneurs for entrepreneurs.

Founded by Marilyn and Jonathan Brathwaite, Mithril delivers private-client-level service to owner-managers underserved by institutional players.

Founders

Marilyn and Jonathan Brathwaite.

Marilyn and Jonathan were both born in the United Kingdom. Marilyn's mother is Barbadian; Jonathan's parents are both Barbadian, and he was raised on the island. They live and work in Barbados, with active operations in Canada and Florida.

Marilyn spent seventeen years at a multinational corporation across the UK, Ireland, and EMEA, managing a P&L in excess of USD 500M with responsibility for contract management, SOX corporate governance, and financial disclosure. For the past six years she has worked with owner-managers on international business and wealth structures, trusts, and operating companies.

Their work focuses on the structures, treaties, and relationships that let Latin American owner-managers operate confidently across borders, with a deliberately small client roster.

Team

A small team. Deep specialisms.

Mithril's senior team works directly with every client. Engagements are partner-led; nothing meaningful is delegated downstream.

Private Client Advisor

Rianna Holas

Rianna leads private-client engagements at Mithril, drawing on over eight years' experience in international corporate services, trust and estate administration, and regulatory compliance. She has a particular focus on turnkey relocation for individuals and families moving to Barbados. As a licensed real estate agent, she guides clients through every stage of the move: property acquisition and rental, immigration and work-permit applications, post-migration settling-in support, and ongoing concierge services.

Alongside relocation work, Rianna advises on company formation, corporate governance, and company administration, and serves as a director on a number of client companies, overseeing statutory compliance, board governance, and regulatory affairs. She also leads AML/CFT compliance for the firm.

Rianna holds a bachelor's degree in Hospitality and Tourism Management and is a member of the Society of Trust and Estate Practitioners (STEP) and the Barbados Association of Compliance Professionals.

In-House Counsel

Dr. Jonathan Brathwaite

PhD, TEP

Jonathan is an international tax lawyer who has worked independently for over fifteen years across the United Kingdom and Barbados, with clients connected to Barbados, Canada, Mexico, Brazil, the United States, and Switzerland. He specialises in compliant, commercially workable cross-border tax structures for owner-managed international businesses, investment funds, and private clients, drawing on a wide range of corporate, trust, and business solutions, and has led service teams to deliver on the advice given.

He holds a Master of Laws (LLM) in International Tax Law from the University of Florida's Fredric G. Levin College of Law and is completing a Doctor of Juridical Science (SJD) in International Taxation at the same institution. He also holds an LLB from the University of Wolverhampton, an MSc in Mathematical Finance from Imperial College London, and a BSc in Business and Computing from Brunel University. Jonathan is an Attorney at Law in Barbados, was called to the Bar in England and Wales, and is a member of the Barbados branch of the International Fiscal Association (IFA).

Offices

Three offices. One standard.

Headquarters

Bridgetown, Barbados

Avondale House, Bank Hall, Saint Michael BB11078

Advisory Office

Halifax, Nova Scotia

Working relationships with senior Canadian professionals supporting USA, LATAM, and Canada flows.

Operating Presence

Miami, Florida

On-the-ground presence for clients operating through the Port of Miami corridor.

Our Approach

Boutique standards. Operator instincts.

Boutique by design.

We work with a small number of clients we know well, and only operate structures we understand.

Treaty-driven structuring.

Cross-border strategy built on the USA-Barbados and Canada-Barbados double tax treaties.

Operator-grade execution.

Practical, commercially sensible structures, set up correctly the first time and operated through the lifecycle.

Private-client service level.

Personal attention typically reserved for ultra-high-net-worth families, applied to owner-managers below the institutional threshold.

Disclaimer & Compliance

Mithril International is not a licensed law firm. Formal legal and tax opinions are delivered by appropriately licensed professionals: our in-house tax counsel and our partner attorneys in the United States and Canada. Mithril sources, drafts instructions to, and liaises with external counsel so clients receive correct advice and have it implemented correctly.

Read why Mithril

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