Groupthink kept collapse warnings outside the planning consensus

Did Britain underestimate the risks in France and Norway because intelligence and government oversight were inadequate?

Not primarily; some analysts recognized the possibility, but a dominant group view treated it as too remote to reshape plans.

Some intelligence personnel recognized the possibility of disaster in France and Norway, but it appeared too remote to alter the prevailing view. Organizations can settle on a majority interpretation that is difficult to change. They may then fit new ideas into that existing worldview. Groupthink can leave planners unprepared even when some warnings exist.