Nuclear defence is historically an emotive issue with the fear being that if a nuclear capability exists then more states will aspire to become nuclear powers and the more nuclear powers there are the more likelihood there is of actual usage of the weapons. However it often seems that the reason for having nuclear capability is more like a badge denoting power than something that can actually be used: as per this quote from Yes Prime Minister.
The debate has arisen again with the government having approved the use of Menwith Hill in North Yorkshire for the 'Son of Star Wars' programme. Ministers gave approval without parliamentary consultation and the anti-nuclear lobby are furious about that fact. The real problem though is the communication problem at the inter-state level. Britain claims that the defence is against rogue states: Iran or North Korea being used as examples. Russia on the other hand see it as a renewal of the arms race.
The problem is that it is fairly obvious that neither Iran or North Korea could actually hit the UK and doubtful their missiles (if they exist) could hit any target that the defence system covers at the current time. So is it an attempt to make the British feel protected? In an era of terrorism probably not! So it remains nothing more than a way of ensuring a seat at the top table in world politics; but given that many nations seem to do very well without a nuclear weapons, an aggressive foreign policy or a position of being a global power, why is such a role so important for Britain?