Small Diagonal with Scarlet, Emerald and Orange Fragments: 1971- January 1975

The artist, writing about the sensations created by colour in 'The Shape of Colour', his Fifth Power Lecture in Contemporary Art in 1973 (published in The Studio International in February 1974), explained, 'As far as the experience of our human eye is concerned - and that, exclusively, is the experience which concerns a painter above all others - colour is shape and shape is colour. As far as pure visual sensation goes colour and shape are always one and the same thing. What we call shape is something that begins to be apparent because there is a place where one colour ends and another begins - and this meeting-place of colours becomes, in our consciousness, an edge, a line, an outline, a profile, a boundary or frontier between two differing colour-areas. I am gazing at an area of apricot-ochre: this apricot-ochre is opaque but luminous and flattish; my eye rapidly traverses this flattish opaque apricot expanse and arrives at a frontier along which the apricot-ochre ceases and a field of violet-blue takes over: this meeting-point of apricot-ochre and violet-blue becomes in our consciousness a thing in its own right, a thing we call 'a line'; and this line - a thing created solely in our vision by the continuousness of the meeting-points of those two fields of ochre and blue - this particular line 'defines', as our verbal language would put it, the edge of a cloud in the sky'.