What Hamilton Insurance Group, Ltd. told the SEC could break it.

As a global property, casualty and specialty (re)insurer (Hamilton Re is a Bermuda Class 4 insurer), Hamilton carries large natural-catastrophe exposure and depends on third-party vendor models (Verisk and Risk Management Solutions) plus its proprietary HARP platform to estimate probable maximum losses. These models rest on broad assumptions (storm surge, demand surge, zone density, secondary uncertainty) and do not capture all perils, so actual catastrophe losses can materially exceed modeled estimates — a core climate/physical-peril exposure that drives earnings and capital volatility. Severity medium: central to the business and partially mitigated by reinsurance/retrocession, but inherently model-dependent.

“For natural catastrophe risk, we rely on third-party vendor models (e.g., Verisk and Risk Management Solutions) and proprietary tools such as our HARP platform to estimate probable maximum losses.”

Hamilton accesses its business almost entirely through insurance and reinsurance brokers, and that distribution is concentrated: its largest brokers accounted for an aggregate ~54% of 2025 gross premiums written (Marsh McLennan ~10%, Arthur J Gallagher ~7%), and within the Bermuda segment the concentration is far higher (Marsh ~41%, Aon ~30%). Because brokers control the flow of business to Hamilton, the loss of, or a deterioration in, a key broker relationship — or consolidation among the major brokers — could materially reduce premium volume. The individually named ≥10% brokers (Marsh, Aon) are captured as edges; this records the channel-concentration risk. Severity medium.

“accounted for an aggregate of approximately 54% of our gross premiums written in 2025, with the largest broker, Marsh McLennan, accounting for approximately 10% of our gross premiums written. The second largest broker, Arthur J Gallagher, accounted for approximately 7% of our gross premiums written.”

37% of Hamilton's investment portfolio (as at Dec 31, 2025) is held in the TS Hamilton Fund, a quantitative strategy managed by Two Sigma, alongside 55% fixed income/short-term and 8% cash. Two Sigma's highly complex and automated processes rely on advanced technology and large datasets, creating risks of coding errors, data inaccuracies, cybersecurity breaches, systems failures and unauthorized trading that could produce unpredictable outcomes and material investment losses. Concentrating over a third of investable assets in a single externally managed quant fund ties a meaningful share of Hamilton's capital and earnings to that fund's performance and operational integrity. The Two Sigma manager relationship is captured as an edge; this records the investment-concentration/operational risk. Severity medium.

“Two Sigma's highly complex and automated processes rely on advanced technology and large datasets, creating risks of coding errors, data inaccuracies, cybersecurity breaches, systems failures and process changes that may lead to unpredictable outcomes.”