In Gwynne Dyer's article "Put nukes away", Dyer lamented over the meaning of 'nuclear deterrence' and the dire state of the UK's economy.
He expressed frustration over the UK keeping in service its nuclear powered Trident submarines and its "retaliation from the grave" capability.
He writes that the four submarines will need to be replaced by 2028, at an estimated cost of up to $30 billion. That is approximately the same cost the Afghan War will have cost the British taxpayer, from its beginning till their withdrawal in 2014.
Currently, the UK has 'second strike' capability, due to the fact that it is much more difficult to locate nuclear weapons on at least one submarine (which is always at sea), than locating a cruise missile that is in "the closest, (which is) safely out of the reach of foolish children".
Maintaining a second-strike nuclear deterrence is likely a much more affordable military insurance policy than maintaining a large conventional force which can inflict comparable damage.
Although a defence force solely orientated around peace-keeping and humanitarian missions may be the most affordable option, it doesn't live up to the two main characteristics of a military 'defence force'. What's more, a true military deterrence relies on the three Cs: communication, capability and credibility.
Without the second strike capability possessed through a tactical submarine force, the UK may be able to communicate, but the capability and credibility wouldn't be there - leaving its deterrence literally 'high and dry'.