A duck, typing: Drying the ceiling

The other day we had a leak from some of the pipework in our bathroom. Fortunately nothing too serious, and the plumber sorted it out quickly (once I'd determined it was beyond my own skills) - but it had dripped through the bathroom floor and the ceiling of the downstairs loo below; a lot of moisture got trapped in the space between the ceiling and the floor above it.

That was going to take a while to dry out on its own, so I rigged up something to create some airflow.

A computer case fan (everyone has these lying around, right?), powered from a USB portable phone charger (via a 5V->12V adapter) - hooked up to the ceiling space (over the hole for the downlighter, which is hanging down from its wire) by a "duct" made from a cereal packet and some duct tape.

Judging from the smell of damp plaster coming from the air it blows out, it's surprisingly effective...