Defence spending cuts are rarely out of the news.  One of the ways of economising is for the UK's Ministry of Defence to spend money on so-called, 'off the shelf' systems.  But there could be problems with that.  In this podcast, Elizabeth Pearson talks to Dr John Louth, Deputy Head of RUSI's Defence Industries and Society Programme.  He's looked into the effects of buying off the shelf - and found it could be a false economy.  I began by asking Dr Louth about the current strategy for Defence buying.