The mouse thingy is not currently plugged in. We have a heater on the landing in the evening, to warm up the rooms and help little bear sleep (it gets his room up to a tropical 15 C which would be fine if he could be persuaded to sleep UNDER the covers). The heater is using the mouse plug.

Besides, little bear has found that the mouse thingy makes an amazing shriek if you press the test button. I found evil cat in a state of complete trauma after forcibly dragging him away from the mouse thingy.

I need to identify another socket for the thingy.