LMX spiral
Category: Market history and reinsurance · Reviewed by the Apex broking team · Last reviewed 2026-08-22 · ~4 min read
Category: Market history and reinsurance
Also known as: London Market Excess of Loss spiral, the spiral, retrocession spiral, LMX
Related concepts: retrocession, excess of loss reinsurance
What LMX means
LMX stands for London Market Excess of Loss: excess-of-loss reinsurance written between participants in the London market, principally Lloyd’s syndicates, on each other’s books. Excess-of-loss reinsurance itself is unremarkable and essential — it is explained under excess of loss reinsurance. What made the LMX market different was that a large share of the business being reinsured was itself excess-of-loss reinsurance, so the layers were being written on layers. Reinsurance of reinsurance is retrocession, and retrocession is where the spiral formed.
How the spiral worked
The mechanism was circular. Syndicate A wrote an excess-of-loss cover and protected it by buying retrocession from syndicate B; B protected its own book by buying from C; C bought from D; and somewhere down the chain a participant bought protection from A, or from someone who had already appeared. When a large catastrophe struck, each participant paid its layer and then claimed on its own protection, so the same underlying loss travelled around the circuit repeatedly. Each circuit added brokerage and reinstatement premium, and the gross amount claimed through the market could be a multiple of the actual economic loss, even though the net loss to the market as a whole was unchanged.
What set it off
A concentrated run of catastrophe losses in the late 1980s and early 1990s tested the structure — among them the Piper Alpha platform explosion in 1988, the Exxon Valdez oil spill in 1989, and a sequence of severe European windstorms and hurricanes. These were exactly the events the excess-of-loss market existed to absorb. The problem was not that the losses were unforeseen but that no participant could see how many times its own capital stood behind the same event.
Why nobody could see it
Two failures compounded. Aggregate exposure monitoring was inadequate: underwriters could not trace, through several layers of retrocession, how much of a given event they had ultimately assumed, and there was no market-wide mechanism to net the circuit. And the incentives ran the other way: writing LMX business produced visible premium income with losses that appeared only when a catastrophe occurred, so the business looked profitable for as long as the weather held. Losses ultimately settled on a relatively small number of syndicates, with severe consequences for the individual Names whose unlimited liability stood behind them.
The aftermath
The spiral was one of several strands — alongside long-tail asbestos, pollution and health hazard liabilities — in the crisis that reshaped Lloyd’s in the early 1990s. The restructuring that followed included the reinsurance of pre-1993 liabilities into a separate vehicle, discussed under Equitas, the admission of corporate capital alongside individual Names, and much stricter control of syndicate underwriting. On the technical side the market moved to realistic disaster scenario testing, formal aggregate and event-limit management, restrictions on writing retrocession of retrocession, and far more disciplined use of the reinsurance to close.
Why it still matters
The LMX spiral is the standard illustration of a risk that is invisible on any single contract and obvious only in aggregate. Every element of it was individually reasonable: each cover was priced, each retrocession was bought prudently, each underwriter was managing their own book. The failure was systemic, arising from the pattern of connections rather than from any one decision. The same shape recurs whenever a market reinsures itself in a closed circle — which is why aggregation and accumulation control, rather than individual risk selection, is the discipline the episode is remembered for. It is also the reason modern discussion of systemic cyber accumulation reaches for this precedent.
Frequently asked questions
What does LMX stand for?
London Market Excess of Loss — excess-of-loss reinsurance written among London market participants, principally Lloyd’s syndicates, on each other’s books.
How did a single loss get multiplied?
Because much of the business being reinsured was itself excess-of-loss reinsurance. Each participant paid its layer and then claimed on its own retrocession, and the chains looped back on themselves, so the same underlying event was presented around the circuit many times.
What did the market change afterwards?
Aggregate and event-limit monitoring, realistic disaster scenario testing, constraints on writing retrocession of retrocession, corporate capital alongside individual Names, and the separation of pre-1993 liabilities into a dedicated run-off vehicle.
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This entry is part of the Apex Insurance Wiki. Last reviewed 2026-08-22. Next review: 2027-02-22. It is general insurance information, not legal advice, and it describes UK market practice and law as at August 2026.
Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This page is general information, not advice on a specific policy.