In an exhibition catalogue at the Marlborough Galleries in 1962, the artist discusses the Sibyl series 'I saw many years ago a curious fungus in the form of flat horizontal shelves growing out in clusters from the tree trunk, which for some reason were exciting and which I had always wanted to incorporate in my own work if the right opportunity came along. The idea seemed appropriate here...this form then worked itself out in the Monitors, Prophets, Sibyls ...growing into a beak-like shape in the more recent work'
(K. Armitage, op. cit., p.3)