Former IG and OvalX Executive Appointed CEO of Flagstone

Arman Tahmassebi has been named Chief Executive Officer of UK-based savings platform Flagstone, marking the latest step in a career spanning more than two decades across brokerage, trading, and fintech firms.

Tahmassebi announced the appointment via LinkedIn, confirming he has stepped into the CEO role after previously serving as Chief Operating Officer at Flagstone. He succeeds co-founder Simon Merchant, who has stepped down from the CEO position for health reasons but will remain involved as Chairman and strategic adviser.

Flagstone operates a digital savings platform that enables individuals, businesses, and charities to manage cash through a single application, spreading deposits across multiple partner banks. The company positions itself as the UK’s largest savings platform, with close to £19 billion in assets under administration.

Tahmassebi joined Flagstone as COO in early 2024 and played a key role in strengthening operational capabilities, scaling the platform, and shaping its long-term strategy. His promotion comes as the firm reports record revenues and continued profitability, closing 2025 with assets under administration up 21% year-on-year.

Prior to Flagstone, Tahmassebi spent over five years at LendInvest, where he served as Chief Operating Officer at the AIM-listed property finance lender. His earlier career includes senior leadership roles at ETX Capital, later rebranded as OvalX, where he held both COO and CEO positions during periods of restructuring and transformation.

He also served as Chief Operating Officer at London Capital Group and spent nearly 15 years at IG Group. His tenure at IG included roles such as Global Head of Operations and Managing Director for Europe and South Africa, overseeing operations, sales, and regional expansion.

In comments following his appointment, Tahmassebi said he plans to build on Flagstone’s strong foundation, positioning cash savings as a strategic asset class for both individuals and businesses as the platform enters its next phase of growth.