The other night, I thought we were being burgled. I crept downstairs, and there was my 17-year-old lying on the sofa in the semi-darkness watching a late-night film.
'What are you doing?' I said.
'Just watching the end,' he said.
'But it's one o'clock in the morning!' I said.
'Is it?' he said equably.
'Aren't you tired?' I said.
He looked up. Silly question. If he'd been tired, he would have gone to bed.
When you have babies, they sleep while you party. When you have teenagers, they party while you sleep. Eventually, when they're about 18, you're going to bed (hot water bottle, bed socks, good book) just as they're getting ready to go out. This feels really weird. Is this the end of the day or the beginning? I'd argue the point but I can't keep my eyes open.
Teenagers, as we know, have different body clocks. Even if they have an early night, they don't really come to until about noon. They become gradually livelier during the day until, at about 10pm, they're quite bright and chatty. 'Is he nocturnal yet?' asked a neighbour when my eldest was 15. It's true - left to their own devices, teenagers are like cats, asleep all day and out all night. (I bet you most of them can see in the dark.)
Every so often our timetables collide. I was sitting in the kitchen one night talking to a very old friend at 4am when my son tiptoed through the front door.
'Oh,' he said. 'You're still up.' I think he would have been less surprised to see Will Smith in a ballgown.
I felt quite proud of myself. We parents haven't got the stamina to do it all the time. But every so often we can be nocturnal, too.
For more of Marianne's must-read weekly column on living with teens, click here.