The critical systems and infrastructure on which our lives and well-being depend are becoming increasingly complex and interdependent. There are challenges for both ensuring and assuring the safety of these complex engineered systems (where by engineered we mean that they are at least partly deliberately designed), when they exhibit many or all of the characteristics of complex systems [1, 2]. These properties include emergence, self-organisation, and nonlinearity. This means that we are unable to predict a system’s behaviours from knowledge about its parts and their interactions alone. These problems are worse for ad hoc systems which arise due to the unplanned interactions or interdependencies of systems that were conceived independently; the coronavirus pandemic has given us many such examples.