Arrests, restraints and detainments of all kings, princes and people, of what nation, condition, or quality whatsoever’ are defined in the Rule for Construction of the Policy (No. 10) as referring to political or executive acts, and not including a loss caused by riot or by ordinary judicial process. As goods were held to be lost when they could not be forwarded to their destination because of these perils (e.g. siege of a city), insurers introduced the frustration clause, the effect of which is to relieve the insurer of liability for a claim based on ‘arrests’ etc.