Arman Tahmassebi, a seasoned operations leader with more than 25 years’ fintech experience, has been appointed Chief Executive Officer (CEO) of Flagstone, the UK’s largest savings platform* with almost £19 billion assets under administration.
Arman succeeds Simon Merchant, Co-Founder of Flagstone, who has decided to step down as CEO for health reasons and does so with the full backing of Flagstone's Board and executive team. Simon will continue to play an active role in the business he co-founded in 2013 as Chairman of the Board and strategic adviser, supporting Flagstone’s leadership as the company enters its second decade of growth.
A highly experienced fintech leader, Arman brings more than 25 years of senior operational and executive leadership at some of the UK’s most innovative financial services businesses. Having joined Flagstone as COO in early 2024, Arman has played a pivotal role in strengthening operational excellence, scaling the platform and shaping the company’s long-term strategy.
Prior to Flagstone, Arman spent five years as COO at LendInvest, the AIM-listed property finance lender, helping to drive growth, resilience and public-company governance. Before that, Arman held senior leadership positions at ETX Capital, first as COO and then CEO, leading the business through periods of transformation and change. Earlier in his career, Arman spent almost 15 years at IG, culminating in three years as Global Head of Operations, where he helped scale one of the UK’s most successful fintech platforms globally.
Simon Merchant, Co-Founder & Chairman of Flagstone, adds:
'Following a thorough and wide-ranging search to identify the strongest possible successor, Arman emerged as the clear choice to lead Flagstone into its next phase. He brings deep fintech expertise alongside proven CEO and COO experience, and over the past 18 months has built a strong understanding of our business, culture and long-term ambition.
'Flagstone is in a position of strength, with a clear strategy and strong momentum. Arman has already become an influential leader internally and is clear about how we can build a leading UK fintech. Arman has my full support and I look forward to working closely with him as Chairman and adviser as the business enters its next phase.'
Arman Tahmassebi, CEO of Flagstone, comments:
'Under Simon’s leadership, Flagstone has grown from a bold idea into a high-growth, profitable fintech that is reshaping how individuals and businesses think about optimising their cash savings. With £55 million in revenue in our last full year and sustained profitability, the platform is well positioned for its next stage of growth.
'I am excited to build on this strong foundation and continue Flagstone’s mission to help savers see cash not simply as a ‘rainy day fund’, but as an asset class in its own right - one that delivers competitive risk-adjusted returns and financial resilience at times of uncertainty.'
The announcement comes after Flagstone closed another year of record revenues and sustained profitability, ending 2025 with almost £19 billion of individuals’ and businesses’ savings under administration - a 21% increase year-on-year. Flagstone’s business savings division saw markedly high growth during the year. In 2025, total cash directly deposited by UK SMEs onto Flagstone’s savings platform for businesses increased by 82%, from £1.7 billion to £3.1 billion.
*Based on the number of banks on the panel and the savings accounts on the platform.
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