GB presented the following explanation :
I can think of a possible but highly unlikely explanation:
There are two possible routes through the pipework for the hot water to reach
your tap. The shorter route got air locked when they drained down the system
to cap off pipes in the bathroom. That left the water to find its way round
the longer route. The air lock sorted itself out overnight, and now the water
is taking the shorter route.

That is the only explanation I would agree with.