A key question in quantum mechanics is “Do quantum effects survive in the large scale limit?”. Answering this question will shed new light on our understanding of fundamental physics. To attack this tantalising problem, we want to create table-top experiments demonstrating the most macroscopic matter-wave interferometry. We will develop towards tests of proposed phenomenological models for the spontaneous collapse of the wave function. Continuous spontaneous localisation (CSL) is one such model. If collapse is detected, our results would galvanise the need to identify as yet unknown mechanisms, phenomena or forces beyond the standard model of particle physics. On the other hand, if our macroscopic quantum superpositions do not collapse, we will have exquisitely sensitive quantum sensors for particle and astrophysics. These sensors could enable the direct detection of undiscovered short-range forces, or a new light field associated with hidden sector, dark matter, quantum gravity or neutrino physics. This dual purpose is a great strength of our approach. To achieve these ambitious goals, we seek to put 10-1000 nm nanoparticles into quantum superpositions of different positions in space. We are a team of 32 scientists at 14 UK universities with regular meetings.