My daughter has always held tyrannical opinions on in-car entertainment. In the early days she would clamour for her Sing-along Nursery Rhymes cassette when Desert Island Discs was about to begin. She has vetoed my Dolly Parton collection in case pedestrians should hear when the windows are down and today, as Aled Jones wafts us along the M25 with my favourite funeral hymns, she insists that he is extinguished so she can make her own music.
'Sticks and stones may break my bones but whips and chains excite me!' she bellows from the back seat. My shrill of horror intrigues her. 'What's so bad?' she asks, genuinely baffled. Intuition tells me that this is one for the Vicar, lying prone in the passenger seat beside me. 'Say something!' I hiss, but the Vicar is evidently formulating his next sermon for he doesn't seem to hear.
I am just improvising an answer involving circus ring masters and fairground rides when I glance in the rear view mirror and notice the eight-year-old making disconcerting gestures. 'Come on, come on, I like it, like it!' he sings. My shrill of horror intrigues him. 'What's so bad?' he asks, but I'm not convinced that his bafflement is genuine.
I announce that from now on that song is banned. 'You can't ban it,' says my daughter, shocked. 'It's Rihanna.' I glance helplessly at the Vicar, but he has now evidently sunk into a state of profound prayerfulness and he doesn't seem to heed.
My daughter resumes her rendition. I can see her watching the back of my head, hoping her defiance will prompt thrilling revelations about this mysterious taboo. I remember my resolution to answer all sensitive questions frankly and wisely when they arise. But I'm dodging Eddie Stobarts on a packed motorway, it's late, I'm tired, my youngest is within earshot and I really really don't feel up to discussing bondage.
Instead I reach for Aled and turn the volume up. 'Just promise me,' I conclude, 'that you won't do any singing in the vicarage when the churchwardens are there.'
What do you do if your children learn inappropriate songs in the school playground or on their iPods? Does trying to ban them - or trying to explain them - increase their appeal? How do I wean a cool ten-year-old off Rihanna and onto Doris Day?