Alan Battersby is, above all, known for his research on the biosynthesis of the "pigments of life" that are built on closely related tetrapyrrolic structural frameworks. His research group elucidated, in particular, the essential role played by two enzymes, deaminase and cosynthetase, in the steps from aminolevulinic acid via porphobilinogen and hydroxymethylbilane to uroporphyrinogen III. The latter is the first macrocyclic intermediate in the biosynthesis of haem, chlorophyll, vitamin B12 (cobalamin), sirohaem and cofactor F430. The work involved the careful study of labelled intermediates, using deuterium, tritium, 13C and 14C placed into potential precursors made by organic or enzyme-assisted synthesis. The most successful strategy was to incorporate the stable isotope 13C into potential substrates, since the outcome of the biochemical reactions (for example giving uroporphyrinogen III) could readily be followed using high-field 13C NMR. The Battersby group's use of doubly-13C-labelled porphobilinogen was especially revealing of the rearrangement step which had puzzled those who wished to understand the details of the biosynthesis of uroporphyrinogen III. Based on these results, Alan Battersby suggested that a spiro-pyrrolenine intermediate was generated at the active site of cosynthetase and to prove this mechanism his group designed and synthesised a spiro-lactam analogue which was indeed shown to inhibit the enzyme.