Radiation damage produces many defects in diamond that are associated with lattice vacancies and interstitial atoms. EPR has proved to be a valuable tool in the characterization of such defects although often detailed models of the defect structure have not been attempted. It is shown that the R1 defect that is characterized using EPR as a defect having S=1 can be interpreted in a highly strained vacancy model where a spin-orbit effect plays a key role. The inclusion of a Jahn-Teller interaction in the model is also discussed and it is shown that this could hold important significance for the D tensor associated with the defect.