Somewhere at the back of my mind, and I'm not sure why, I know that batteries don't work well below a certain temperature. Maybe it's from having owned, until recently, an old Land Rover that discharged its battery at the first hint of frost. Or maybe some of those science lessons from years ago actually sunk in.

Something that definitely did sink in was the need to have a smoke alarm and wherever I have lived I have always had one. Princess Pea is no exception. Except that in this case, the smoke alarm also warns me of cold weather.

 A month or so ago I was woken at 4am by an annoying beeping noise that I soon realised was the infuriating chirping sound that the alarm makes when the battery is low. Deciding that it was too cold to get up, I shoved a pillow over my head, resolved to look at it in the morning and went back to sleep. The next morning there was not a peep from the smoke alarm and a subsequent push of the test button showed me it was still working.

In the early hours of the following morning the same thing happened. This time I took the smoke alarm off the wall, shoved it under the duvet and went back to sleep. Once the sun came up, for the briefest of moments, I wondered why I had a smoke alarm in bed with me. Then the fuzzy memory returned. I tested the silent smoke alarm. It still worked. Later that evening, for good measure, I set the smoke alarm off when I opened the  door of the log burner just as a gust of wind blew the smoke back down the chimney. It was definitely working and it frightened the life out of me. It also proved that I shouldn't take the battery out until I had bought a new one.

Yet that night I was still woken up at an unearthly hour by the same plaintive beeping of that bloody alarm. Again I got out of bed, grabbed the alarm and shoved it under the duvet. I could not fall asleep again straight away and I listened to the muffled, sorrowful peeps of the alarm. And then they stopped. Had those temperamental batteries finally given up? I pressed the test button and the resulting clamour sent the cat flying.

The fourth night was a repeat of the third. As I listened to the muted beeps from under the covers it slowly dawned on me: the batteries in the alarm were suffering from the cold. As the temperature inside the caravan dropped the current output of the batteries slowed until the alarm sent out signals that the batteries weren't working properly. In the morning, or indeed under the duvet, the temperature would increase sufficiently to make the batteries work once more.

Not bad reasoning for 4am.