Dr Jimmy Walker worked as a Scientific Leader in water microbiology and decontamination at Public Health England (PHE), Porton UK. He has 30 years’ experience in public health microbiology with an extensive publication record, and regularly attended national and international scientific conferences. His particular interests were the presence of opportunistic pathogens in hospital water systems and advised hospitals on incidents and outbreaks associated with waterborne pathogens such as Legionella spp., Pseudomonas aeruginosa and Mycobacteria spp. He worked closely with the Department of Health (DH England) and Health and Safety Executive in writing and developing national and international guidance on the microbiology of water and decontamination in healthcare.