In the last few years we have entered the “golden era” of observational cosmology. The standard cosmological model, LCDM, is a very good fit to the data. However, low redshift large scale structure probes seem to point towards a slower growth of density perturbations than Planck + LCDM would prefer. This can be due to some unaccounted systematic effects, or an indication of new physics! Assuming the latter just because it’s easier to do so, and leaving the hard work to investigate the former to highly skilled people that never get the credit they deserve, I will show that the tension can be alleviated by a dark energy – dark matter interaction with pure momentum exchange. In my talk I will first summarise the current state of the CMB-LSS tension, and introduce interacting dark energy – dark matter theories. I will then present a comprehensive statistical analysis of a pure momentum exchange model using the wealth of available data and show that such models are prime candidates for reconciling the CMB and LSS measurements.