Stone Sentinel: Marex Group ($MRX) Investment Case

In its Q2 2026 letter to partners (“Risk before reward,” dated July 3, 2026), Stone Sentinel Capital (“SSC”) highlights Marex Group Limited ($MRX) as a new long position initiated earlier in the year that the firm says contributed the majority of the portfolio’s returns during the period. Stone Sentinel views Marex, a non-bank derivatives clearing and prime brokerage firm, as significantly undervalued by a market it believes misreads the company as a “commoditized mid-market broker” rather than recognizing what the firm calls its structurally advantaged position in clearing. The firm frames the position within its broader stated philosophy of favoring unpopular, low-expectation stocks over popular ones, noting that despite a 60% year-to-date gain in the shares, it still views Marex as cheap and disfavored.

Business Overview

• Stone Sentinel describes Marex as more than a standard mid-market broker, providing clearing of derivative trades in addition to standard prime brokerage services
• The firm characterizes clearing as a “sleepy back-office function” that is nonetheless immensely profitable, citing 50% pre-tax profit (PBT) margins
• According to the letter, Marex traces its roots to the bankrupt Refco, was initially capitalized by Marathon Asset Management before private equity (largely of Lehman descent) took control, and was built through a series of acquisitions before going public in 2024

Track Record and Capital Efficiency

• SSC notes that over the past decade Marex increased revenues by a factor of 9 and EPS by a factor of 11
• The firm highlights that ROE increased roughly 5x, from 5% a decade ago to 26% last year, which it describes as a rare and desirable improvement in capital efficiency
• Despite this track record, the firm notes the stock has traded at only a low double-digit P/E, which it attributes to the market’s mischaracterization of the business

Competitive Position: Structural Advantage in Clearing

• Stone Sentinel explains that the largest banks are also the largest clearing firms, but that capital regulations make clearing a low-return business for them, since minimum leverage-ratio requirements force banks to hold significant capital against the margin balances clearing requires — capital that could otherwise fund higher-returning businesses like investment banking and lending
• As a result, the firm says large banks limit clearing services to their largest clients (who compensate via other high-fee business), leaving small and medium clients to seek clearing elsewhere
• The firm states that as a non-bank clearing firm, Marex requires 80–90% less capital than large banks to support clearing, allowing it to generate much higher ROE serving clients that large banks reject
• Stone Sentinel notes smaller clearing firms face rising fixed costs (technology and compliance) as exchanges upgrade connectivity, latency, and risk-management requirements, while Marex benefits from scale as one of the top 10 clearing firms globally (8 of the top 10 being large banks)
• The firm points to Marex’s margin balances growing 50% over the past two years, versus low-to-mid-single-digit growth at large banks, as evidence of this dynamic, and describes clearing clients as structurally unable to bypass clearing firms without incurring higher margin costs

Management

• The firm notes CEO Ian Lowitt, former CFO of Lehman Brothers, owns a 3.6% stake in the company
• Stone Sentinel notes that private equity owners (largely of Lehman descent) still hold roughly 9% of the company, which the firm expects to be pared down over time
• The letter notes that heads of various business segments have served as CEO at different points in Marex’s evolution, which SSC characterizes as evidence that senior management holds deep knowledge of the entire business

Valuation

• Stone Sentinel states Marex shares have risen 60% year-to-date but views the stock as still cheap and disfavored at roughly 12x forward P/E
• The firm believes the market continues to give insufficient credit to what it sees as Marex’s structurally advantaged position relative to both large-bank and smaller non-bank competitors

Stone Sentinel Capital views Marex as a rare combination of an improving, highly profitable business — evidenced by its expanding ROE and margin-balance growth — trading at a valuation the firm believes still reflects the market’s outdated perception of the company as a commoditized broker rather than a structurally advantaged clearing franchise. Despite the stock’s strong year-to-date performance, the firm continues to see meaningful upside as the market re-rates the business toward what it considers a more appropriate multiple.

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