The key to an understanding of the National Gas Turbine Establishment at Pyestock lies, perhaps, in the large engineering bias of the professional scientific and technical staff of this advanced research and development organisation, of whom over eighty per cent are engineers by training, so that in every direction the thirst for knowledge and the pursuit of novel techniques is tempered by engineering judgment. For example, even among the specialists, materials science is not narrowly equated with crystallography, chemistry or metallurgy, but is considered largely as the art of exploiting all likely materials to maximum advantage in air breathing propulsion systems.