The review, led by Treasury Chief Secretary Danny Alexander, said there are alternatives to the UK's current nuclear stance which requires at least one nuclear-armed submarine always to be at a sea.
However, it accepts that cutting the size of the current four-vessel fleet would not offer the same degree of resilience as the current continuous-at-sea deterrent and would not guarantee "a prompt response in all circumstances".
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The family of the police officer who was murdered in the Westminster attack have thanked those who were with him 'in his last moments'.
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