I had noticed the woman in the shop, but hadn't really thought anything of her. She was watching me as I tried to keep an eye on Alex, my hyperactive 2 1/2-year-old son, while at the same time picking my way through the kids' section to find a new jacket for him.

She drew a little closer, I noted out of the corner of my eye. She was in her mid-40s, I guessed, wearing a smart trouser suit and carrying a leather bag on one arm. And she was definitely following me round the store.

Now, I'm not of a nervous disposition, but this was unsettling, to say the least. After all, as far as I know, I've never been trailed by a middle-aged woman. But the papers nowadays are full of the oddest stories, so I called Alex out from behind one of the racks of clothes and we prepared to escape.