The day a firm’s single largest claim breaches the primary limit is the day it discovers whether its excess layer was bought properly or assembled in a hurry.
Excess layer professional indemnity sits above a primary policy and responds when claims erode or exhaust the primary limit. For most professional firms the primary policy alone is enough — but a meaningful minority of firms need more. Single large client engagements, mandatory regulator-set primary limits that no longer reflect commercial reality, and contractual demands from sophisticated buyers all push firms into an excess tower. The mechanics of how the layers sit together is where most placements go wrong. Follow-form wording, drop-down provisions on aggregation, and the alignment of retroactive dates and notification clauses across the tower are the questions that decide whether a £5m claim is actually a £5m recovery.
An excess layer is a separate insurance policy that responds only after a defined attaching point — almost always the limit of the primary layer — has been eroded. It does not respond to claims that settle within the primary limit. It does not pay defence costs that fall within the primary. It is dormant cover that only matters in the worst scenarios, which is why brokers and buyers tend to spend less time on it than the primary. That is the wrong way round.
The typical structure for a UK professional firm is a primary policy of £1m, £2m or £5m, with one or more excess layers stacked above it. A solicitors’ firm subject to the SRA Minimum Terms must hold a minimum primary limit of £2m (or £3m for incorporated practices), and many firms buy an excess layer to take the total tower to £5m, £10m or higher depending on transaction size and client demand. A RICS-regulated surveying practice has tiered minimum limits depending on fee income and may sit at £1m primary with excess layers for residential work where Building Safety Act 2022 exposure is in play. Engineering and architectural firms working on commercial projects routinely sit at £5m or £10m towers driven by contractual requirements from main contractors and developers.
The economics of excess layers are favourable to the buyer when the risk is well-presented. Excess capacity prices at a small fraction of the primary rate because the probability of attachment is materially lower. A £5m excess of £5m primary may price at 30% to 50% of the primary premium even though it doubles the tower limit. That ratio is not a guarantee — markets harden, claims experience deteriorates, and specific sectors such as residential design have seen excess capacity tighten significantly since the Grenfell Tower fire and the Building Safety Act 2022 — but the principle that excess capacity is cheaper per pound of cover holds across most professional segments.
The risk in the structure is wording continuity. Each layer in the tower is a separate contract with potentially different conditions. A buyer who assumes the excess layer mirrors the primary is exposed to any gap between the two.
Excess layer wordings fall into two broad categories. Follow-form policies adopt the terms and conditions of the underlying primary policy, with carve-outs for matters specific to the excess layer such as the attaching point and the limit. Standalone policies are written on the excess insurer’s own form and rely on the buyer to align the cover with the primary by negotiation.
Follow-form is the safer position for most buyers but it is not absolute. A follow-form wording typically follows the primary as to terms and conditions but reserves the excess insurer’s own definitions, exclusions and conditions where they conflict. Reading a follow-form policy without reading the primary is meaningless. Reading both, and checking that the excess insurer has not silently varied a key definition such as “claim”, “professional services” or “circumstance”, is essential.
Aggregation is the area where excess layers most often deliver less than expected. The primary policy applies its limit of indemnity to each claim or, in some wordings, to each aggregated series of claims. An excess layer that follows the primary’s aggregation clause will respond consistently. An excess layer that has its own aggregation clause may treat the same underlying matter differently — for example, treating multiple claims arising from a single piece of advice as one claim under the primary but as separate claims under the excess, with the excess limit applying separately to each. The principles in AIG Europe Ltd v Woodman [2017] UKSC 18 govern the interpretation of “related matters or transactions” in aggregation clauses, and the Court of Appeal’s reasoning in Spire Healthcare Ltd v Royal & Sun Alliance Insurance Plc [2022] EWCA Civ 17 confirmed that a single cause can aggregate multiple claims into one limit. The implications for an excess tower depend entirely on whether the layers share an aggregation approach.
Drop-down provisions matter where the primary insurer becomes insolvent or otherwise fails to pay. A well-drafted excess layer will drop down to respond as if the primary had paid in full, preserving the buyer’s position. An excess layer without a drop-down provision leaves the buyer self-insuring the primary limit if the primary insurer cannot pay. The Third Parties (Rights against Insurers) Act 2010 gives third party claimants direct rights against an insolvent insurer’s portfolio, but it does not solve the problem of an excess layer that refuses to engage until the primary limit has actually been paid out.
Retroactive dates and notification clauses must be aligned across the tower. An excess layer with a later retroactive date than the primary creates the same gap problem at the excess level that a misaligned renewal creates at the primary level — except that no one notices until the claim breaches the primary limit. The notification clause in the excess layer should require notification on the same trigger as the primary, and a notification properly made under the primary should be deemed notification to the excess.
A medium-sized consulting engineer holds a tower of £2m primary and £8m excess of £2m, total tower £10m, on a contract requirement from a Tier 1 contractor on a large infrastructure scheme. Primary premium is £45,000. Excess premium is £22,000. The primary wording is from a well-known PI insurer. The excess is written on the excess insurer’s standalone form with a follow-form clause.
A claim arises in 2025 alleging negligent design on a series of related elements across the project. The claimant pursues five separate heads of loss totalling £9m. The primary insurer aggregates the heads of loss as arising from one originating cause and applies a single £2m limit. The excess insurer does not aggregate — its standalone wording defines “claim” by reference to the cause of action rather than the originating cause and treats the five heads as five separate claims, each subject to the excess attaching point of £2m. The result is that the £7m above the primary is treated as five claims of varying size, only one of which exceeds £2m, and the excess layer responds only to that one claim less the attaching excess.
The firm faces a coverage gap of approximately £4m because the aggregation provisions in the two layers do not align. Had the excess been bought on a true follow-form basis with explicit alignment on aggregation, the £10m tower would have responded to the full claim. The premium saving on the standalone wording was £6,000.
Treat the excess layer as a full placement exercise, not an afterthought tagged onto the primary. Issue a clear instruction to the broker to align wording, retroactive date, notification clause and aggregation across the tower.
Ask for a written comparison of the primary and excess wordings, with each material difference flagged. A two-page comparison table is sufficient and should be a standard deliverable from the broker.
Test the excess capacity for financial strength. A weaker insurer at the excess level is acceptable only with a drop-down provision and clear evidence of reinsurance.
Confirm the aggregation position with both insurers in writing if the firm has any exposure to claims series — multiple clients on the same product, multiple matters arising from one piece of advice, or multiple buildings on one development.
Notify circumstances upwards through the tower. A notification made only to the primary may not bind the excess if the wording requires direct notification.
Apex’s view: a properly structured excess tower is one of the highest-value placements a broker can deliver, and one of the most commonly mishandled. The mistakes are predictable — wording mismatch on aggregation, retroactive date drift, no drop-down — and they only emerge when the claim is real. We push every excess placement onto a follow-form basis where possible, accept standalone wordings only with explicit alignment in writing, and insist on a side-by-side comparison of every layer in the tower. The saving on a cheaper excess wording is almost never worth the coverage risk at the moment that limit is needed.
Apex Insurance Brokers serves UK professional services firms and commercial businesses. Call 0117 325 0027, email hello@apexinsurancebrokers.co.uk, or request a quotation.
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