The contingency nobody wrote down

Every plan contains an assumption about what will not go wrong. Most of the time the assumption holds, which is exactly why nobody writes it down.

A school sports day is a useful small example. The plan lists events, times and staff. It assumes the field is dry, the public address system works, and the person holding the stopwatch turns up. None of these appears anywhere in the document, because they are not part of the plan; they are part of the background the plan rests on.

When one fails, the failure is described as bad luck. Frequently it is a contingency that could have been written down in one line. The test that separates the two is simple: could somebody have named this in advance? Rain in June could. A teacher breaking an ankle on the morning could, in the sense that somebody will sometimes be ill. A lightning strike on the shed could not reasonably.

Useful contingency planning is therefore not about imagining disasters. It is about listing the three or four things the plan silently depends on and writing one sentence for each. The sentence does not have to be clever. 'If it rains, the sprints move to the hall and the long events are cancelled' takes ten seconds to write and saves an hour of argument in the rain.

The reason this is rarely done is that writing it feels like expecting failure. It is the opposite: it is the only way to stop a predictable problem from being treated as an unpredictable one.