In September 1996 the United Nations Information Directorate (UNIDIR) held a press conference in Geneva to announce the successful negotiation of a treaty, the Comprehensive Nuclear Test Ban Treaty (CTBT), that when it enters into force will ban all nuclear explosions. At the request of the UNIDIR, Peter Marshall of the Blacknest Seismology Group of the Atomic Weapons Establishment (AWE) joined the panel to answer technical questions from the press (Figure 1). Why was Peter amongst all the experts who had attended the negotiations chosen to join the panel? Because all the delegates recognized that through his personal qualities and his expertise Peter contributed more than anyone else to the success of the technical negotiations. Professor Dr Peter Wille (German Delegation) expressed what many delegates felt:

Peter was able to make such a significant technical contribution to the negotiations because he had worked on the application of seismology to the verification of arms-control treaties, that is, forensic seismology, from its beginnings.