The colours — it must be said — are marvellous. In recent years Twombly has set himself loose from the disciplined pastel palette, dominated by red and white, in which he worked most of his long life (he is 80 this year). Here, circles of roughly painted orange, purple and red throb against a background of smooth and saturated turquoise. The archetypal Twombly sensation, that a bit of a page of sketch book has been massively enlarged into a monumental painting, is in full effect.