The long-wavelength macromolecular crystallography beamline I23 is a unique facility for solving the crystallographic phase problem, using the small anomalous signals from sulphur or phosphorus which are present in native protein or RNA/DNA crystals. This is of increased importance for projects where protein labelling to introduce anomalous scatterers is not feasible. In addition, the beamline's wavelength range provides access to the M-edges of elements, with huge anomalous signals offering new opportunities for phasing large molecular complexes.