The Guardian’s top story is on the future of British nuclear weapons, based on comments by former Lib Dem minister, Sir Nick Harvey. It indicates a less-than-stellar understanding of the subject by the paper:
Harvey said past policy on Trident had been dictated by the 1980s view that the only deterrent to a nuclear attack from the then Soviet Union was the belief that the UK could “flatten Moscow” in retaliation. This led to the UK building Trident and having at least one armed submarine at sea every hour of every day since.
This phrasing misses the point about “Continuous at Sea Deterrence” (CASD). The point of CASD was not that it was necessary to inflict a certain amount of damage, but that “a surprise attack on Western Europe by the Soviet Union was a central driver for UK force planning” (Chalmers, p2).
Nick Harvey’s suggestion that “the Russia of the 21st century […] might find all sorts of damage to be unacceptable short of flattening Moscow” is both reasonable and slightly besides the point : CASD is not about what Britain needs to inflict on Russia, but what assumptions are made about what Russia can and might do to Britain.
As Malcolm Chalmers points out (see piece cited above), the assumption is indeed changing in favour of the view that “the UK homeland does not face a significant threat of attack by other states. Nor, it is assumed, could one emerge without an extended period of strategic warning”. The point, in other words, is not that Russia is more deterrable today, but that the prospect of a Russian first strike has receded.
The second problem with the article is its discussion about the prospect of a non-deployed arsenal:
Instead of replacing Trident with a like-for-like 24-hour nuclear armed submarine presence at sea after the current system is due to be taken out of service in 2028, cheaper alternatives are being considered. These range from stepping down the patrols, to designing missiles to be launched from aircraft, surface navy ships or land, to a delayed launch system on the model employed by other countries, including Japan.
Er, what? “Delayed launch system”? There are all sorts of strategic, technical and financial reasons why alternatives to Trident might be problematic. But, regardless of where one stands in that debate, the comparison to Japan is just bizarre. The paper explains Harvey’s suggestion like this: “the UK would store the warheads in a secure military location, from where they could be removed, put on the tip of a missile and put to sea within weeks or months”.
This is nothing like Japan. In fact, this passage demonstrates a serious confusion between (1) nuclear latency, (2) a rapid breakout capability, and (3) a non-deployed arsenal.
(1) Japan is latent because it has “made large investments in a civilian nuclear power industry, without developing the sort of expertise that would allow the quick assembly of a nuclear device, or the production of delivery vehicles”. Its access to plutonium, technological sophistication, and satellite launch experience mean that it could hypothetically build a deliverable nuclear bomb – but we’re talking years. Clearly, this isn’t what Harvey means.
(2) Rapid breakout refers to the possibility of quick assembly, but minimal attention to delivery systems and the suchlike. An example would be India in the late 1980s and 1990s. From ~1986 onwards, it is presumed that India could easily and quickly put together a bomb. But it couldn’t properly drop this from a plane, or put it on the tip of a missile. India only carried out its first “fully instrumented aircraft drop test” of a bomb in 1994, roughly eight years after preparing a bomb. I don’t think Harvey is suggesting that Britain just wings it like this.
(3) A non-deployed arsenal is similar, but it requires a higher degree of integration and preparation e.g. the fissile core might be stored separately to the warhead, as Pakistan claims of its arsenal, but the warhead would otherwise have to be ready to go (“for a rainy day”, as Harvey quaintly puts it). This is what Harvey means by “put on the tip of a missile”. He envisions the possession of bombs that are basically together, and fully functioning delivery systems – including options like cruise missiles.
Depending on the delivery system, this requires a far higher degree of weapons development  and operational planning for alerting procedures than is suggested by the comparison with Japan. The analogy is fundamentally misleading.
 E.g. “Any programme to develop and manufacture a new cruise missile would cost far more than retaining the Trident D5 missile. In capability terms, cruise missiles are much less effective than a ballistic missile […] Therefore it was clear that, in terms of both cost and capability, retaining the Trident D5 missile is by far the best approach” – Defence White Paper: The Future of the United Kingdom’s Nuclear Deterrent, December 2006, p25