The basic idea is to try to prevent an accident in the first place with appropriate safety factors but then to limit the progress and consequences if one should occur.

Such developments depend on the modern view that knowledge and information is sets of layered patterns in our computers and in our brains.

Engineering is, in its most general sense, turning an idea into a reality – creating and using tools to accomplish a task or fulfil a purpose.

How do engineers actually deal with risk?

The characteristics of each layer emerge from the interacting behaviour of the components working in the layer below.

So resistance is a loss of energy perhaps due to ambiguity and conflict. Capacitance is an accumulation of our ability to do things or to perform. Inductance is our capacity to adapt and innovate.

The over-stretched balloon represents an accident waiting to happen.

humans make mistakes, and natural hazards, such as earthquakes, do occur. So they often have back-up, or contingency, plans – this is known as defence-in-depth.

‘Swiss cheese’ model. He represents the various barriers that keep a system from failing, such as good, safe technical design, alarms, automatic shutdowns, checking and monitoring systems, as separate pieces of cheese with various holes that are the hazards. The holes are dynamic in the sense that they move around as they are created and destroyed