This article presents a parametric study that uses the finite element (FE) method to analyse the problem of long-term settlements following twin tunnel construction in low permeability clay. Similar ground conditions to those typically found in central London, UK, were modelled. The construction process of the tunnels was simulated and thereafter a special boundary condition was used, enabling the FE model to consider the tunnels as fully permeable drains during the post-construction period. Several tunnel depths and separations were studied. The long-term interaction between the tunnels and the manner in which the long-term displacements -both vertical and horizontal - developed, were analysed. Conclusions are drawn about the principal factors that drive these movements. Finally, the potential building damage associated with the short and long-term movements obtained from the FE analyses is assessed, compared and discussed.