Over a print-out of the picture in its current state (as seen above) I make another drawing. It shows how I am gamely trying to control the present while predicting the future and tinkering with the past. Such diagrams of shifting thought rapidly become palimpsests, as from a pictorial Satnav unreliably installed, of pathways rejected almost as soon as they are proposed.

The encounter I recently described, where paranormal planes of colour rise disembodied out above the picture’s surface until the whole work seemed to be made of shimmering veils, now seems less disconcerting. Finding that the phenomenon is not unique to this painting has helped. I discovered that a picture I have been working on in my Oxford studio produces the same sensation. It only needed a short stare to make this canvas in its turn yield up similar hovering illusions of depth. This picture, also long worked on and as yet untitled, is painted in the manner of a mosaic. In a sense it is a study for the work I am doing in Westminster Cathedral. The insistent patterning of the tesserae engenders in this case its own layer of black, a spidery phantom which floats well free of all other colours, as if to illustrate Dr Johnson’s wittily abstract definition, in his great dictionary, of a net... ‘anything reticulated or decussated at regular intervals with interstices between the intersections.’

Mosaic Painting, in progress, 2008.