One nondescript Monday morning when I thought I was doing nothing, a refugee sentence slipped into my mind. 'Suddenly, as if at a signal, all the leaves began quivering slightly.' What was this? Where had it come from? Might it be one of the subtle forest phenomena - possibly the herald of a summer shower? - to be found in Turgenev's Sportsman's Sketches, which I had recently been reading? But this is a pure guess. It could have come from anywhere or nowhere.

Still, I thought, now that it's here, what is the least effort one needs to make in order to transform it utterly? Let's see. Change a single letter and at once we reach: 'Suddenly, as if at a signal, all the loaves began quivering slightly.' Loaves, I suppose, need not be much less natural than leaves, particularly if it's early in the day in, say, Montmartre - (ah, Montmartre! I really must see it before one of us packs in!) - but already the sentence is clinging by few or no fingertips to the natural world. Besides which, these are not particularly interesting loaves, are they?

Substitute 'twigs' for 'leaves' and not much changes. However, substitute 'branches' and already it sounds much more uncanny. Go one step further up, to 'trees' - and, a little oddly, it's again less weird, perhaps because 'trees' is interpreted as a general way of referring to leaves and twigs, whereas branches mysteriously insist ...