The picture posed great technical problems for Hockney. He worked out the composition over an extended period of time, from photographs and drawings. This two-sided sketch contains a three-quarter profile portrait study of Clark, made from life, on the recto. Also on the recto, but in reverse, is an ink sketch of a head. On the verso, scratched through, is a profile ink sketch of Birtwell, but it may not be a preparatory study for the double portrait. Hockney wrote: 'The figures are nearly life-size; it's difficult painting figures like that, and it was quite a struggle. They posed for a long time, both Ossie and Celia. Ossie was painted many, many times; I took it out and put it in, out and in. I probably painted the head alone twelve times' (Stangos, p.203).
Shortly after its completion in 1971, the finished portrait was displayed at the National Portrait Gallery, London, together with all the preparatory drawings and photographs. The Tate owns two other studies for the painting (Tate Gallery T01516-17).
Nikos Stangos (ed.), David Hockney by David Hockney, London 1976, pp.23, 197, 203-4, 239
Marco Livingstone, David Hockney, revised edition, London 1987, pp.131, 136-7, 159