It’s half past ten and I’m violating a fairly strict boaty rule: no engine running after eight. You can hear the big diesel rumble several boat lengths away, but as there is no one on board either in front or behind me, I am hoping I can get away with it, just this once.

When I don’t run the engine for a couple of hours a day the batteries reproach me in the morning. The charge needle dips below 12 volts and little red lights let me know I have done wrong. If I need any further nudging there’s the alarm that screams when the batteries are feeling malnourished and I happen to plug in my computer.

The batteries don’t care when they get their kicks, but experienced boaters shake their heads and cluck and mumble about efficiency and alternators if I switch on before nightfall, which leaves a narrow opportunity for doing right. I have begun to think that having five leisure batteries is not all that unlike having a husband and four children: I am expected to be home by six to do my duty.

I wasn’t home by six today, either to charge the batteries or to feed the fire, and I spent most of the hours I was away, not enjoying myself as I ought to have been (because it was my birthday), but in the John Radcliffe Hospital Accident and Emergency Department.

To while away the time I counted up how often I had already visited emergency rooms with my children. It’s a number so big I don’t like to confess to it, especially as one of my four has never contributed (touch wood), except as an innocent bystander.

Five broken bones and five foreign objects in the eye seem like the kinds of problems even a well-regulated, if a little unlucky, largish family might have. But there were at least half a dozen other ER visits, most of the complaints more exotic, like chlorine gas poisoning. I bet you didn’t think I was going to say that.

My youngest is responsible for more visits than all the others combined (including the chlorine incident). She’s especially not good with head injuries, having responded to her first toddler bump by holding her breath until she turned blue, went rigid, and passed out.

She went on as she had begun, though I only took her to the ER for that particular problem once. It was quite impressive when she did the blue rigid unconscious sequence in public and I had to restrain onlookers from calling ambulances first and child protection services next (apparently parental ennui at a comatose child is anti social and objectionable).

My Baby fell and banged her head on Sunday, and a few days later in the ER it was déjà vu all over again, except that this time she was almost all grown up and very funny while we waited for the radiographers and the neurologist. She didn’t pass out, but she did bump into things and she got several doctors upset.

Her mother was upset too.

The doctors were puzzled enough to keep her there for many hours, but not quite puzzled enough to bring out their expensive kit (MRI). They relaxed when they finally came up with a theory: Benign Paroxysmal Positional Vertigo, brought on by a blow to the head. (They especially liked it because it was benign, and I liked it too, only I would have liked it better if they had done the MRI first.) Then they let her go home, because they had no solutions. BPPV is very hard to treat, they noted sadly.

When she was a toddler, and it became clear that she passed out not just because she was hurt but also because she was cross, I asked the doctors what I should do. They shrugged and suggested I try not to upset her.

I don’t think we know a lot about the human brain.

But batteries are quite another matter. I’m thinking of trading mine in for another model.