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There is no specific legislation that requires this sort of disclosure on restaurant or catering menus in England or Wales.
Neverthelss, such disclosures are regularly made by restaurants in order to reduce the likelihood of them becoming liable for damages in the event of a choking injury. Whilst they cannot limit or exclude liability for death, a claimant must first prove negligence (and a warning to the customer that the fish may contain bones is often used to mitigate the risk.
Similarly, if the food is described in a manner that suggests that there are no bones (such as a fillet) it could potentially have the opposite effect, exposing the restaurant to a greater chance of being held liable if bones are discovered and cause injury.
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