Category: Insurance case law · Reviewed by Amy Price, Account Executive · Last reviewed June 2026
Reinsurance authority addressing aggregation and the unifying factor required to compress multiple losses into a single claim under treaty wording.
The case formed part of the body of reinsurance litigation arising from the long-tail US liability claims that drove much of the late-twentieth-century reconstruction of the London market. American Centennial Insurance Co, a US-domiciled cedant, had reinsured part of its book with INSCO Ltd. Disputes arose over the application of the reinsurance treaty wording to losses arising under the underlying business, including questions about how losses were to be aggregated for the purpose of the reinsurance limit and the operation of any per-event or per-occurrence threshold.
The underlying losses included exposures of a kind familiar from the period — asbestos, pollution and other long-tail US liabilities — and the cedant sought to present losses to the reinsurer aggregated in a manner that maximised recovery within the structure of the treaty. The reinsurer responded by challenging the cedant’s aggregation methodology, the unifying factor relied on, and the scope of “follow the settlements” obligations that might have constrained the reinsurer’s ability to dispute aggregation.
The wording in dispute, as is common in this period of reinsurance, contained an “event” or “occurrence” formulation governing per-loss limits and aggregation. The court was asked to construe that wording in context and apply it to the patterns of underlying claims presented by the cedant.
[Note: detail in this section is given at a general level because exact factual citations have not been verified. Researchers are referred to the report at [1996] LRLR 407 for the full procedural and factual record.]
The principal issues for the court included: (i) the proper construction of the aggregation wording in the reinsurance treaty, in particular the meaning of “event” or “occurrence” as a unifying factor; (ii) whether the cedant’s aggregation methodology was permissible as a matter of contract; (iii) the operation of the “follow the settlements” clause and its impact on the reinsurer’s ability to challenge aggregation decisions taken at cedant level; and (iv) the burden of proof on the cedant in establishing that losses fell within the aggregation criteria.
A further issue concerned the interaction of aggregation language with the cedant’s claims-handling practices and the extent to which a reinsurer must accept the cedant’s classification of losses where that classification is reached in good faith and in a businesslike manner.
The court addressed the proper construction of the aggregation wording and the limits of “follow the settlements” in the reinsurance context. Applying conventional principles of contractual construction, the court approached the aggregation language with reference to its ordinary meaning, the commercial context and the relevant precedents on “event”-based aggregation.
The court emphasised that “follow the settlements” provisions, while important, do not give the cedant carte blanche to determine the operation of aggregation language. The reinsurer remains entitled to challenge the cedant’s classification of losses where that classification depends on a contestable question of contractual construction, and the court will not subordinate the reinsurance contract’s express terms to a generalised duty to follow the cedant’s lead.
On the facts, the court reached conclusions about how the aggregation wording applied to the underlying losses and what unifying factor was required for losses to be compressed into a single reinsurance claim. The case is often cited in the context of the developing law on how reinsurance treaty wordings respond to long-tail US liabilities and how aggregation interacts with claims cooperation and settlements clauses.
(Detailed quotation is avoided here as exact wording has not been verified. The report at [1996] LRLR 407 should be consulted for the precise reasoning. [verify citation])
In reinsurance, aggregation language using “event” or similar wording is construed according to ordinary contractual principles. “Follow the settlements” provisions do not displace the express aggregation language: a reinsurer is entitled to test the cedant’s classification of losses where aggregation is in issue, provided the challenge goes to a genuine question of contractual construction rather than to second-guessing the cedant’s good-faith business decisions.
American Centennial v INSCO is among the body of cases that shaped the modern understanding of aggregation in the London reinsurance market. It is regularly cited alongside Insurance Co of Africa v Scor and Hill v Mercantile and General on the relationship between aggregation, follow-the-settlements and the reinsurer’s right to scrutinise the cedant’s classification of losses.
For reinsurance buyers, the case is a reminder that even broad follow-the-settlements language does not bind a reinsurer to accept aggregation positions that depend on contestable construction questions. Cedents should expect challenge where the unifying factor relied on is unusual or where the aggregation methodology departs from market practice.
For reinsurers, the case provides authority for testing aggregation classifications and resisting cedant-driven loss bundling that does not match the wording. It supports a structured approach to disputes: identify the aggregation language; identify the unifying factor relied on; test the cedant’s classification against the wording and the precedents.
For brokers, the case underlines the importance of clear, consistent aggregation language across primary, excess and reinsurance layers. Mismatches between cedant-level aggregation and reinsurance-level aggregation can produce significant uninsured exposures. The reinsurance market and the broker’s wording team should work together to ensure consistency where possible.
The case also continues to be cited in modern London market disputes about treaty wording and the proper limits of follow-the-settlements.
By Matt Bartlett, Director, on 2026-06-06. Next review: 2026-12-06.
This entry is part of the Apex Insurance Wiki. Last reviewed by Matt Bartlett on 2026-06-06. Apex Insurance Brokers Limited, FCA FRN 724952, Companies House 07014570. Not regulated advice — consult your broker on your specific position.
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