Sophy follows my eyes around her yurt, with its clothes and cotton nappies hanging like bunting from the inside walls, the woodburner, the packed-mud floor covered with rugs of indeterminate hues, its plate rack full of drying baby dishes, the low bookshelf full of cast-off paperbacks (impossible to read without full daylight), the one light bulb hanging down. ‘But I don’t need anything,’ she protests. She takes another sip of her herb tea. She says she is drinking it because she is used to bitter tastes, and sage discourages milk production, and that she knows that now Noah is almost one she must make an effort to get to that scary place called ‘out there’ again.

I look at Spike, wondering how much longer he is going to put up with living in a bender with a lactating single mother who can afford only pulses and legumes, a screaming baby and no TV, when all his friends from school live in lovely new boxy houses with rectangular white walls, hard flat floors, and something called ‘plasmas’, or lovingly restored three-hundred-year-old vicarages, mills or farmhouses.

According to Mirabel, when Spike comes home from school, ravenous at four fifteen, to ask what’s for tea, Sophy always answers, ‘Lentil surprise’, and Spike apparently always says, ‘My favourite,’ even though there’s nothing remotely surprising about her garlic and onion lentil bake and he has it every day.

I am being extra-nice to Sophy, asking her if she needs anything, because we are about to leave, even though the herbal heritage session goes on for another hour. I give the signal to the children, who muster with alacrity by the entrance, which beckons to us like a triangle of light in the pitchy gloom of the yurt. And then Sophy’s eyes fall on the woodburner, to where smoke is seeping out of a crack in the iron gullet that feeds outside. Then her eyes flash. ‘Well, a new chimney, perhaps.’

Sophy zips up the snowsuit and replaces Noah on the floor. He sits motionless for a couple of seconds, and then sets off in a fast crawl over the packed earth of the bender towards the aperture and the world beyond, to get even dirtier and muddier, and to discover yet more new and pleasant objects to pop into his gummy mouth.

Sophy watches his progress as she might a wind-up toy: with detachment, and a curiosity about where it might fetch up. She wonders, as she must do, oh, only about every ten minutes or so, how she is going to do this, every day, for the next eighteen years, on her own, and hopes this desperation doesn’t show in her eyes, but it does. I really feel for her.

‘I know what I need,’ Spike mutters, eyeing Mirabel. ‘Flat walls. A floor. And then, perhaps, a PS3.’