when least expected
At the point in time at which one is least prepared or has not been anticipating (something). Things seemed to be going well, and then, when least expected, my boss said that I was being fired. We will organize our forces and strike the enemy when least expected.
when least expected
when one does not expect something. An old car is likely to give you trouble when least expected. My pencil usually breaks when least expected.
when least expected
When something is not awaited, as in My brother always calls when least expected, or You might know that the furnace would break down when least expected-we just had it overhauled .