David Cameron: 'We believe in Trident'

David Cameron has insisted the government remains committed to the renewal of the Trident nuclear deterrent.

But he also said it was right to consider whether the current programme offered value for money.

Britain's nuclear weapons system is made up of four submarines, based at the Faslane naval base on the Clyde, which can deploy Trident ballistic missiles carrying nuclear warheads.

At least one submarine is always at sea so a continuous deterrent can be maintained.