When Def Stan-00-55 (MOD 1997) was declared obsolete on 29 April 2005, there was an expectation that Def Stan 00-56 would provide guidance on how to develop and procure safety related software. That has proved elusive despite a number of attempts to provide the MOD with material that would assist its suppliers of safety related software. However, Def Stan 00-55 continued to be one of the most frequently downloaded defence standards and coupled with the MOD’s need for clarity and consistency when procuring safety related software, it has been decided to re-issue the standard. This paper provides an insight into the rationale and main drivers behind its re-introduction and focuses on the principles and strategic intent of the standard compared with its predecessor.