Duncan McColl is a practising member of the International Association of Precision Therapists, the International Society for Professional Hypnosis (USA) and is a biofeedback, behavioural and management science consultant. He served as a pilot in the RAF during World War II, later qualifying as a chartered accountant.

He spent forty years abroad, chiefly as a senior financial and marketing executive in American multinational companies, visiting some fifty countries, and qualifying as a behavioural science instructor and Gestalt therapist. Since 1982 he has worked as a hypnoanalyst and has provided training in precision analysis for experienced therapists and medical staff from Britain and overseas.