Green began hunting ghosts in the early forties and was known for his attempts to study ghosts from a scientific perspective. His paranormal investigations were interrupted by two years of National Service in the army, but as soon as he was finished he began his paranormal career. In 1949, Green founded the Ealing Society for Psychical Research and in 1952 he co-founded the Lewisham Psychic Research Society and the National Federation of Psychic Research Societies; he continued his ghost investigations. During this time he also carried out ESP investigations and tested mediums. Nothing came of this research.
