The ability of coupled climate models to reproduce the observed interannual variability, such as that associated with El Niño – Southern Oscillation (ENSO), is crucial for the detection of long-term climate variability and its change. Several coupled models have, in the past, demonstrated a reasonable skill in simulating ENSO-like behavior in the tropical Pacific, though they have struggled to capture the observed amplitude and periodicity. This talk describes the spatial and temporal structures of ENSO simulated by a recent version of the UKMO unified model. The main focus is on the physical mechanisms responsible for the existence of the ENSO variability in the coupled model, with a particular emphasis on the lead-lag relationships with sea surface temperatures in the southwestern Pacific.