His research has focused on cell signalling. He has studied intracellular calcium as a cell regulator for over 50 years, pioneering the application of Ca2+-activated bioluminescent proteins to measure free Ca2+ in live animal, plant, bacterial, and archaeal cells; he has published books on intracellular calcium as a universal regulator. At the Marine Biological Association laboratory in Plymouth during the 1970s, he studied the bioluminescent hydroid
Obelia geniculata. As a result of research on deep-sea bioluminescent organisms on the research ship RRS Discovery, he discovered that
coelenterazine is the substance responsible for bioluminescent in at least eight phyla –
Cnidaria,
Ctenophora,
Protozoa,
Chaetognatha,
Mollusca,
Arthropoda,
Echinodermata,
Chordata, and that
bioluminescence is the major communication system used at great ocean depths. Since 2000, his research focus has been
lactose, and
food intolerance, which has led to a new hypothesis on the cause of irritable bowel syndrome, and the mystery illness which afflicted
Charles Darwin for 50 years but was never cured. He has written or edited 12 books, and over 250 peer-reviewed papers on intracellular calcium, bioluminescence, lactose and food intolerance. In 2020, he published his first novel
Mirror Image; what Darwin missed, a scientific mystery based in Anglesey. ==Awards==