We all know what people can and can't do, how they are built, what the limits of the human body are, yet some images challenge the brain and create illusions.

For most, the word yoga conjures images of pretzel-like body postures.

Many of the poems in my next book are influenced by the artist Helen Chadwick, whose early work made much use of images of her own body – until a change in the late 1980s.