Dale Wigley has made major contributions to the biochemistry of enzymes that are active in DNA replication and repair. His work at the interface between structural biology and enzymology adopts a creative synergy that has allowed him to elucidate several important and novel mechanisms. This is exemplified by the first crystal structures of a DNA helicase that, surprisingly, showed the protein was active as a monomer, a view that challenged the established dogma that helicases must function as oligomers. Subsequent work elucidated the detailed mechanism of these enzymes and explained the strategies by which different helicases promote DNA unwinding.