She doesn’t use the doorbell. When doorbells don’t get answered, it’s impossible to know whether that’s because there’s no one home, or the individual she’s looking for is heading out the back door as she’s standing at the front, or maybe the bell is broken. Knuckles eliminate the last possibility. She raps on the glass, and immediately a dog begins to bark – a yappy terrier, her least favourite kind. Within a moment, a woman’s ineffectually telling it to be quiet, but the dog’s ignoring her, scratching at the door to get at the visitor. Naylor hears muttering, the rattle of keys, and a firmer order for the dog to go to its bed. Surprisingly, the barking stops as it complies. A key turns in the lock, and a chain is taken off the latch.

The woman who opens the door is enormously overweight. The journey down the hallway seems to have winded her, and she’s breathing as heavily as if she’d run a mile, leaning on a stick held in a hand wearing three diamond rings, all pressing into the flesh of her fingers to such a degree, Naylor thinks they must be painful. And yet she might be attractive; she looks no more than forty, and she’s made an effort with her hair and clothes, which, though voluminous, are all matched as an outfit.

Naylor holds up her ID.

‘Mrs Birch? Sheila Birch? DS Rachel Naylor, Thames Valley Police. Do you mind if I have a word?’

‘Police?’ asks Mrs Birch. ‘What’s it about?’

‘Just a routine enquiry. May I come in?’

Sheila Birch holds open the door, and Naylor steps inside. The house is beautifully kept, the carpets vacuumed, the paintwork freshly white, with a strong scent of lavender potpourri from a bowl on the sill of the tiny hall window.

‘We can go in the lounge,’ says Mrs Birch, limping and wheezing as she leads the way. ‘I’ve put Oscar in the kitchen. He’s not very good with visitors.’

‘Sounds like he makes a good guard-dog.’

‘He’s a Jack Russell and all mouth. He doesn’t even come up to my knee, and I’m not tall. I don’t suppose anyone would find him very scary. Have a seat.’

Sighing with effort and breathlessness, she lowers herself into a fireside chair which appears to be of abnormally large proportions. On a side table, she has all her home comforts: the TV remote, a Samsung tablet, a mobile phone in a candy-pink case dotted with fake gems. Naylor takes a seat opposite, in a normal-sized armchair. Mrs Birch props her stick against the chair arm and looks expectantly at Naylor.

‘I’ve a few questions, if I may, regarding a vehicle you own which was recently reported stolen. An 09-plate Ford Focus. Is that your car?’