Thought for the Day seeps into her unconscious, reminding her that it is time to leave. 'In some ways, God is like an iPod…' She puts her plate and cup in the sink and leaves down food for her cats, Sparky and Flint. As she does so, she answers the ever-present sardonic interviewer in her head. 'OK, I'm a single, overweight woman on my own and I have cats. What's the big deal? And, OK, sometimes I do speak to them but I don't imagine that they answer back and I don't pretend that I'm any more to them than a convenient food dispenser.' Right on cue, Flint, a large ginger Tom, squeezes himself through the cat flap and fixes her with an unblinking, golden stare.

'Does God feature on our Recently Played list or do we sometimes have to press Shuffle?'

Ruth strokes Flint and goes back into the sitting room to put her papers into her rucksack. She winds a red scarf (her only concession to colour: even fat people can buy scarves) round her neck and puts on her anorak. Then she turns out the lights and leaves the cottage.

Ruth's cottage is one in a line of three on the edge of the Saltmarsh. One is occupied by the warden of the bird sanctuary, the other by weekenders who come down in summer, have lots of toxic barbecues and park their 4 x 4 in front of Ruth's view. The road is frequently flooded in spring and autumn and often impassable by midwinter.

'Why don't you live somewhere more convenient?' her colleagues ask. 'There are some lovely properties in King's Lynn, or even Blakeney if you want to be near to nature.' Ruth can't explain, even to herself, how a girl born and brought up in South London can feel such a pull to these inhospitable marshlands, these desolate mudflats, this lonely, unrelenting view. It was research that first brought her to the Saltmarsh but she doesn't know herself what it is that makes her stay, in the face of so much opposition. 'I'm used to it,' is all she says.