Complex sentence: He was posted to head an RAF team at the Atomic Warfare Research Establishment to participate in the development of the British atomic bomb and in 1957 he was made senior RAF advisor for the development of the H-bomb.
Split into simpler sentences: He was posted to head an RAF team at the Atomic Warfare Research Establishment to participate in the development of the British atomic bomb. In the 1950s he was senior RAF advisor for the development of the H-bomb.