I was accosted by an oddly-dressed, dribbling fat man outside the Salvation Army shop this morning. He began tugging excitedly at my sleeve while pointing at something in the shop window. 'Lobbilob!' he exclaimed.

'Pardon?'

'Lobbilob!'

'I'm sorry, I - '

'Lobbilob!'

Why does this kind of thing keep happening to me? In the window was a video of shark movie Open Water and it was at this that the man seemed to be pointing. I gritted my teeth. 'Do you require assistance?' I asked.

'Lobbi akks nams lobbilob.'

I breathed a huge sigh of relief when a middle-aged woman came out of the shop holding the video and handed it to the fat man, making him dribble even more. 'Here you are, Duncan,' she said gently. Turning to me, she asked, 'He wasn't bothering you, was he?'

'Oh, no, I just didn't . . .'

'He loves these kinds of films,' she said, awarding me a smile.

I thought for a moment. 'Are you sure this movie will be suitable?' I asked her. 'I've seen it; it's truly awful. It isn't Jaws, you know.'

'Oh he won't watch it, dear,' she said quickly, 'He stores them under his bunk-bed. He's got hundreds of fish videos and shark DVDs - it's just his way.'

'That explains everything,' I felt like saying, but didn't.

On the way home, an idea occurred to me. 'Tuna salad for lunch, Audrey.' I told my little companion.