As public sector debt soared and a cash-strapped MoD found itself increasingly squeezed, there were new calls for the UK to re-examine the case for renewing its submarine-based strategic deterrent. But were there any credible alternatives? In March 2007 a vote in the UK parliament endorsed government plans to renew the independent strategic nuclear deterrent by constructing a new generation of nuclear-powered ballistic missile submarines (SSBNs) and buying into the US Trident D5 missile life extension programme. Since that time, work had begun on concept design activities for the so-called Successor submarine and it’s Common Missile Compartment (the latter being engineered under a joint US/UK project).”