Flagstone Appoints Fintech Operations Specialist Arman Tahmassebi as New CEO

Flagstone — one of the UK’s largest savings and fintech platforms — has named Arman Tahmassebi as its new Chief Executive Officer (CEO), marking a strategic leadership transition that comes at a critical moment in the company’s growth trajectory. Tahmassebi succeeds Simon Merchant, the co-founder of Flagstone, who is stepping down from the CEO role for health reasons while remaining actively involved as Chairman of the Board and strategic adviser.

The appointment underscores Flagstone’s commitment to scaling its operations, advancing technology-driven savings solutions, and deepening its footprint in a competitive UK fintech landscape characterised by sustained demand for high-yield cash management tools, streamlined customer interfaces, and robust regulatory compliance frameworks.

A New Chapter for Flagstone

Flagstone was launched in 2013 with the mission of reimagining cash savings — enabling individuals and businesses to access and manage savings across a range of leading banks and building societies through a digital, streamlined platform. Over the past decade, it has grown into one of the UK’s largest independent savings platforms, with nearly £19 billion in assets under administration.

Under Merchant’s leadership, Flagstone achieved consistent revenue growth and expanded its product suite, particularly for business and organisational savers seeking better risk-adjusted returns than those available through traditional bank offerings. In 2025, the platform reported record revenue and profitability, with an £55 million turnover and strong year-on-year growth of 21 percent in assets under administration.

The board’s decision to tap Tahmassebi as CEO reflects a desire to build on this momentum while leveraging his deep operational and strategic experience. His appointment follows a thorough and wide-ranging search — one that the company says identified him as the strongest candidate to lead Flagstone into its next phase of growth and innovation.

Arman Tahmassebi: From Operations Specialist to Chief Executive

Arman Tahmassebi brings more than 25 years of senior leadership experience in financial services and fintech operations to the CEO role. Prior to his appointment, he served as Flagstone’s Chief Operating Officer (COO), a role in which he was instrumental in strengthening operational excellence, scaling the platform’s infrastructure, and shaping the company’s long-term strategic vision.

Before joining Flagstone in early 2024, Tahmassebi held several senior positions across respected financial and fintech firms. He spent five years as COO at LendInvest, the AIM-listed property finance lender, where he played a key role in driving growth, operational resilience, and governance — critical components for a public company navigating challenging market conditions.

Prior to that, he held leadership roles at ETX Capital, including COO and then CEO, guiding the business through transformation and change. Earlier in his career, Tahmassebi spent almost 15 years at IG Group, culminating in three years as Global Head of Operations — a period during which he helped scale one of the UK’s most successful fintech platforms across global markets.

This breadth of experience — spanning scaled operations, leadership transitions, and strategic execution — positions him uniquely to steer Flagstone through both opportunities and challenges in the evolving savings and fintech landscape.

Upon his appointment, Tahmassebi remarked that he was excited to build on Flagstone’s strong foundation and help savers view cash not merely as a safety buffer but as an asset class capable of delivering competitive, risk-adjusted returns.

Leadership Transition: Balancing Continuity and Change

Simon Merchant’s decision to step down from the CEO role — while remaining Chairman — underscores a leadership transition built on continuity rather than disruption. Merchant co-founded Flagstone with a long-term vision for transforming savings and has remained closely involved in its strategic development.

In support of the transition, Merchant said that the board’s choice of Tahmassebi was based on his deep operational expertise, understanding of Flagstone’s culture, and alignment with the company’s ambition to scale responsibly. Merchant’s continued presence as Chairman and adviser offers stability and strategic continuity during the leadership handover.

This dual leadership model — with an experienced founder in a governance role and a proven operational leader at the executive helm — is becoming increasingly common in fintechs that have matured beyond early startup phases. It allows organisations to benefit from strategic guidance, while empowering seasoned operators to manage day-to-day execution and market positioning.

Flagstone’s Position in the UK Fintech Landscape

Flagstone operates in a competitive segment of the UK financial market where digital platforms are transforming traditional savings and cash management. The company’s ability to aggregate access to competitive savings rates through a user-friendly interface has resonated with both retail users and business customers, particularly in a low-interest environment where savers seek more efficient yield opportunities.

In the business savings arena, Flagstone has seen particularly strong traction, with deposits from UK SMEs growing markedly — evidence that demand for platform-driven cash management solutions is robust. This positioning is now being reinforced under Tahmassebi’s leadership, as he brings a sharpened focus on operational excellence and platform scalability.

The UK’s fintech ecosystem is also characterised by rapid innovation in digital banking, payments, embedded finance, and savings solutions. Fintech firms of Flagstone’s scale face pressures from both regulatory evolution and shifting consumer expectations. Against this backdrop, an experienced CEO with deep operational capabilities provides a strategic advantage — especially one who has navigated diverse business cycles and technological shifts.

Strategic Priorities Under New Leadership

While an early phase of Tahmassebi’s tenure will likely focus on consolidating Flagstone’s current strengths, several strategic priorities are expected to shape the coming chapters:

1. Scaling Platform Capabilities

As Flagstone continues to serve both individual and business customers, investments in technology — including risk management, user experience, and scalability — will be central to sustaining growth.

2. Expanding Product and Market Reach

With a leadership team experienced in broader financial services, Flagstone may explore partnerships, new product features, or deeper integration with emerging fintech ecosystems.

3. Enhancing Operational Resilience

Given Tahmassebi’s operational background, strengthening governance, compliance, and operational resiliency — particularly in a post-pandemic, tightly regulated environment — will likely be a priority.

4. Strengthening Customer Trust

With continued profitability and strong asset growth as a backdrop, Flagstone’s focus on delivering value and transparency for savers will remain crucial to its brand positioning.

Looking Ahead

Arman Tahmassebi’s elevation to CEO comes at a time when fintech firms face intensified competition from digital banks, embedded finance providers, and regulatory shifts that demand adaptability and resilience. His extensive experience across operations and leadership roles positions him well to navigate this complex landscape while building on Flagstone’s core strengths.

Flagstone’s journey from a startup savings platform to a significant player in the UK fintech savings ecosystem reflects both strategic execution and an ability to innovate within traditional financial sectors. With almost £19 billion in assets under administration and continued revenue growth, the company enters its next decade with momentum — and a leadership team poised to convert operational expertise into market expansion and product evolution.