The Large Synoptic Survey Telescope (LSST), will revolutionise our understanding of the extragalactic variable sky by discovering millions of transient detections per night. The key to fully exploiting this exciting science will be rapid spectroscopic classification of transients, combined with a systematic and unbiased follow-up strategy. The Time-Domain Extragalactic Survey (TiDES) has secured a quarter million fibre hours on 4MOST (4-metre Multi-Object Spectroscopic Telescope) to follow up LSST-era transients and their host galaxies (see Swann et al. 2019) . We present an overview of the science aims and goals of TiDES as well as details of our simulations predicting the success of our rapid spectroscopic follow-up programme. TiDES will generate the largest ever sample of spectroscopically confirmed supernovae (SNe), including tens of thousands of cosmologically useful SNe Ia and their host galaxy properties.