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This Royal Navy footage shows the successful firing of an unarmed Trident missile from HMS Vigilant during a test.
- Trident is a sea-based ballistic missile system that comprises the UK’s nuclear deterrent.
- It can be fired at targets up to 7000 miles away.
- At its fastest, each missile can travel at over 13,000 miles per hour.
- Four Vanguard nuclear submarines can carry 16 missiles each.
- Their power is estimated as the equivalent of eight Hiroshima nuclear bombs.
- From 2028, the Vanguards will be replaced by Successor submarines.
- The submarine replacement is estimated to cost between £15bn and £25bn.
Source: Royal Navy and Ministry of Defence
Liberal Democrat MP Sir Malcolm Bruce has voiced concerns about funds being diverted away from conventional military equipment to pay for Trident.
He told Sky News: "We do accept the case for a nuclear deterrent and we are not in favour of unilateral disarmament".
"But we also recognise that the cost of a nuclear deterrent is extremely high.
"There are many people inside the Ministry Of Defence and the Armed Forces who desperately want to ensure that we have the latest and most up-to-date conventional equipment.
"[They] would be extremely concerned if that was prejudiced by a very heavy commitment to a budget for replacement of a nuclear deterrent which by definition is not used, as opposed to weaponry which they need".
Shadow defence minister Kevan Jones has said it is "absolutely right and necessary" for the UK to retain an independent nuclear deterrent, but it must take into account the costs involved.
The Prime Minister's pro-stance on nuclear weapon is the opposite to that of Scottish First Minister Alex Salmond who is anti-nuclear.
Mr Salmond has said that if Scotland gets its independence nuclear, his SNP party will not allowed nuclear weapons to be based there.
Recently, Mr Salmond said: "What won't happen in an independent Scotland will be getting dragged into illegal wars, having Trident nuclear weapons dumped on the Clyde for another 50 years".
Prime Minister David Cameron will be in Scotland today and will host a PM Direct event at a defence contractor based in the West of Scotland.
Mr Cameron has said he is still committed to keeping defence jobs in Scotland.
He has also warned it would be "foolish" for Britain to consider abandoning its Trident deterrent because the UK faces an increased threat of a nuclear attack from regimes including North Korea.
Mr Cameron will also visit HMS Victorious, one of the Royal Navy's Vanguard-class submarines, to welcome home her returning crew from their 100th patrol.
The Prime Minister says he is still committed to keeping defence jobs in Scotland in a plea for voters to remain part of the UK.
The defence sector employs 12,600 people in Scotland, amounting to around 0.5% of the working population, David Cameron will tell workers at a Scottish defence contractor today.
The jobs include shipbuilding, manufacturing, and making components for jets which are sold to foreign countries.
"Defence matters, and defence jobs matter," Mr Cameron said before his visit.
"Scotland has a world renowned and highly skilled defence sector that employs over 12,600 people and has annual sales in excess of £1.8 billion."
For Labour, shadow defence minister Kevan Jones said it was "absolutely right and necessary" for the UK to retain an independent nuclear deterrent, but it must take into account the costs involved.
"World events demonstrate that in an unpredictable era our country needs the ultimate security guarantee," he said.
"The precise nature of the deterrent must be judged on meeting military capability requirements and cost."
In an article written in the Daily Telegraph, David Cameron has said Iran was continuing to defy the will of the international community over its nuclear programme while North Korea may already be building a nuclear arsenal.
"The highly unpredictable and aggressive regime in North Korea recently conducted its third nuclear test and could already have enough fissile material to produce more than a dozen nuclear weapons," he said.
"Last year North Korea unveiled a long-range ballistic missile which it claims can reach the whole of the United States. If this became a reality it would also affect the whole of Europe, including the UK."
He went on: "Does anyone seriously argue that it would be wise for Britain, faced with this evolving threat today, to surrender our deterrent?
"Only the retention of our independent deterrent makes clear to any adversary that the devastating cost of an attack on the UK or its allies will always be far greater than anything it might hope to gain."
The Prime Minister has warned it would be "foolish" for Britain to consider abandoning its Trident deterrent because the UK faces an increased threat of a nuclear attack from regimes including North Korea.
In an article for The Daily Telegraph, he has written:
Mr Cameron adds that in his judgment, it would be "foolish to leave Britain defenceless against a continuing, and growing, nuclear threat."
Latest ITV News reports
David Cameron said the UK needed to maintain its nuclear deterrent after claiming that North Korea could launch a missile attack on Britain.