Glasgow, Scotland - It is a multibillion-pound weapons system that is praised by its supporters and derided by its critics.

Britain's ageing nuclear deterrent, known as Trident, which is based at HM Naval Base Clyde on Scotland's west coast, is today under the spotlight as attention turns towards a parliamentary vote to endorse the principle of its replacement.

This month saw Michael Fallon, the UK defence secretary, announce a £642m ($910m) spend on the programme's renewal, which, coming months before any vote is likely to be called, took the money already invested in the project to almost £4bn ($5.6bn).

On February 27, tens of thousands of protesters filled the streets of London to show their opposition to the renewal of the system, which is currently made up of four Vanguard-class submarines carrying Trident missiles.

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Leading the demonstrators were two of Britain's most high-profile anti-nuclear politicians - opposition Labour Party leader Jeremy Corbyn and Scotland's first minister and leader of the Scottish National Party (SNP) Nicola Sturgeon.

It is the recent rise of both figures in British politics - Corbyn when he unexpectedly won the Labour leadership last September and Sturgeon when her anti-nuclear (and pro-Scottish independence) SNP gained 56 out of 59 Scottish seats in last May's UK general election - that has put the question of Trident's renewal into sharper focus.

Timothy Edmunds, a professor of international security at the University of Bristol, told Al Jazeera that these "two new features" have given the debate an "openness … with perhaps more potential to change things than at any point in a long time.

"The other new feature, of course, is that this is the first decision to renew a nuclear weapons system for the UK that has taken place outside of the context of the Cold War," continued Edmunds. "So there are the two domestic political reasons and a broader strategic difference that have given the debate a slightly different character."

Scottish First Minister Nicola Sturgeon, in red, joins anti-Trident demonstrators on a march organised by the Campaign for Nuclear Disarmament entitled 'Stop Trident' in London [Andy Rain/EPA]

A costly vanity project

The ruling Conservative Party of Prime Minister David Cameron is overwhelmingly in favour of replacing Trident with four new Successor submarines at an estimated cost of £41bn ($58bn).

Yet the voices of 56 strident anti-nuclear SNP politicians (up from six SNP MPs in the 2010 UK general election) have added political weight to the discussion.

But Corbyn's lifelong unilateralist convictions - despite bolstering the SNP's Trident position in parliament - have caused deep rifts within his own party.

Labour's current UK-wide official policy is to support renewal - but in January Corbyn dropped pro-Trident Maria Eagle as his shadow defence secretary in favour of an anti-Trident replacement who is now heading a review of the party's defence policy.

To complicate matters further in the British Labour family, Scottish Labour revealed its own opposition to the programme's renewal at its annual party conference last November.

The dynamics of party politics apart, the re-emergence of the nuclear debate has re-ignited passionate arguments on both sides of the divide.

For anti-nuclear campaigners, who were left angered by Fallon's pre-emptive spending move, Trident (and its potential replacement) is seen as an economic obscenity and an affront to humanity.

With US Defence Secretary Ash Carter indicating last month that Britain's place as a global power largely depended on its retention of nuclear weapons, many activists view the system as nothing but a vanity project.

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"The major threats that we face today are climate change and terrorism, and nuclear weapons do nothing to deal with that," said Arthur West, the chairman of the Scottish Campaign for Nuclear Disarmament (SCND).

He told Al Jazeera that Michael Portillo, a former British Conservative defence secretary who served in the post from 1995 to 1997, was one of an "increasing number of people with military and defence experience who are saying that [Britain's nuclear deterrent] doesn't serve any military value".

A matter of prestige?

From Britain's pro-nuclear perspective, such arguments cut very little ice. Peter Sandeman is one Trident advocate who believes that its replacement with Successor is a military and security necessity - no matter what the cost.

"The biggest single argument for [Trident and its replacement] is Russia," said Sandeman, who is the editor of Save the Royal Navy - an independent online platform that strives to highlight the concerns of Britain's naval warfare force. He said that it was alarming how often reports emerged of Russian aircraft nearing British airspace or its vessels sailing close to British territorial waters.

"To me, and although people talk about the Cold War being over, I would argue that we are effectively in another kind of Cold War already," the editor said. "Russia, which is the largest nuclear armed state in the world and is investing more in nuclear weapons, is a serious threat to us."

Edmunds, however, questions whether Britain's retention of nuclear weapons is a key factor in the country with the fifth largest economy in the world remaining a major player on the international stage. 

While possessing nuclear weapons "does have a certain element of prestige or status in international politics," Edmunds said, "it seems a jump to then say that British prestige is necessarily dependent on Trident [or its replacement].

"Prestige can be gained in other ways - like championing disarmament, for example," added the academic. "So these are matters of political judgment and there are arguments that can be made from all sides."

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A protest against the Trident nuclear missile system in London on February 27 [Kevin Coombs/Reuters]

De-nuclearisation effects

When the Commons vote for Trident's renewal is eventually scheduled by the prime minister, the parliamentary arithmetic is likely to favour the system's multibillion-pound replacement, which, suggested a January poll for The Independent, is also supported by a narrow majority of the UK public.

The British GMB Trade Union - which boasts more than 600,000 members - recently claimed, too, that thousands of jobs depended on the continuation of Britain's nuclear deterrent. Indeed, the UK government's present spend on the update will make it harder to abandon the project, say some analysts.

The British state has seen its fair share of political surprises in recent years, with the rise in support for Scottish independence in Scotland despite the SNP's independence referendum defeat in September 2014, and Corbyn's victory in the UK Labour leadership election from the position of rank outsider.

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With the UK's forthcoming in/out EU referendum also causing political uncertainty, the prospect of another surprise in the form of a parliamentary vote that would signal a wish to scrap Trident's replacement would, for pro-nuclear campaigners, take Britain into alarming territory.

"As well as severely weakening our defence capability it would have a massive industrial impact," stated Sandeman. "It would have a huge impact on the whole structure of the Royal Navy … and it would take at least a decade before we felt any financial benefit because the cost of de-commissioning [Trident] would be huge .... It would cause absolute chaos."

Tens of thousands of people turned out to support the anti-Trident campaign in London  [Paul Hackett/Reuters]

Follow Alasdair Soussi on Twitter: @AlasdairSoussi

Source: Al Jazeera