Mary Dejevsky: Is it Trident or nothing, after all?

If Britain is, as it seems, intent on retaining its status as a nuclear power, then the vulnerability argument in all its aspects has to be addressed

One of the most conspicuous fault-lines between the two components of our coalition government concerns the future of Britain's supposedly independent nuclear deterrent, Trident. From my injection of the word "supposedly", you might deduce that I am sceptical of the whole project: both retaining and renewing it – and you would be right. I fail to understand why a country of Britain's size and limited wealth should, now the Cold War is over, still want to conceive of itself as an independent nuclear power.

There are other reasons to oppose the renewal of Trident, too, while stopping short of unilateral nuclear disarmament. The first is that it hitches our security (and a part of our weapons' systems) to the United States for the foreseeable future. I favour a common European defence, as being geographically and culturally more rational. A second is the message sent to non-nuclear states when a cash-strapped medium-sized country, such as ours, so stubbornly clings to its nuclear status. And a third is the expense. Even spread over 25 years, £100bn is a great deal of money to earmark for a single aspect of defence. Is it not high time to rethink our priorities?

There is a fourth reason, too, though it is perhaps less well defined. To persist with Trident is to look backwards; in 20, even 30, years, when the renewal becomes operative, the world could look quite different. Think of how defence technology and Britain's overseas commitments have changed even in the past decade. Is it really sensible to invest so much in a future where Britain's current concerns and the whole use for nuclear deterrence may well have been overtaken?

There, in outline, are the broad arguments against renewing Trident, if, like me, you are neither a pacifist nor a unilateral disarmer. Only a few days ago, however, I was in the audience at Chatham House, also known as the Royal Institute of International Affairs, to hear what was described as "a view from the US" on the future of the UK's nuclear deterrent. It was presented by Franklin Miller, a super-venerable and super-organised defence specialist, who was an adviser to George Bush on arms control and also worked for the two previous administrations (those of Bill Clinton and George Bush senior). He now describes himself as an independent consultant, and sits on a range of US government and other advisory boards.

In a crisp 30 minutes, Miller laid out a cogent set of arguments explaining why it was in the interests of Britain to renew Trident – as the last Labour government, and now the Conservatives, have proposed. In so doing, Miller threw down the gauntlet to all who would choose some version of a "Trident-lite". His very clear arguments set the standard; they are the ones that those of us who oppose full renewal will sooner or later have to knock down – if we can.

First, he drew the distinction between "vulnerable" and "invulnerable" defence systems. He assessed all alternatives to the submarine-based Trident system as "vulnerable", in the sense that they would be easily tracked. This would apply whether they were land-based, sea-based (on the surface), or air-borne. The only way to render an air-borne system less vulnerable than it would otherwise be would be to keep it permanently aloft. The expense would be phenomenal, and even then it would be vulnerable, even without the very real risk of an accident.

Second, if it has to be an underwater system, can it be any more modest (i.e. cheaper) than a straight renewal of Trident? Cutting the number of submarines from the current four to three, or even two, has been mooted. In fact, the last government withdrew one from service to save money. How many you actually need, Miller said, is a matter for the top brass and the politicians, but he suggested that three and a spare was the bare minimum to keep the deterrent always available and in service.

As for the option favoured by Lord Owen and, it is believed, some senior military people, to substitute much shorter-range cruise missiles for Trident missiles, this could seriously restrict the flexibility gained from global submarine patrols.

Why not, then – third – a "just in time" system that could be activated only when a threat arose? Miller offered two counter-arguments: the difficulty of ensuring operability at the precise time you needed it and, more to the point, the practical impossibility of sending a submarine (or any other vessel) to sea in secret. The mere rumour of a launch, he said, risked precipitating panic, or even inviting a pre-emptive attack. Rather than enhancing national security, Miller argued, the opposite would be the case. The idea was, as he put it, "completely unsound".

Fourth, on cost, Miller argued that Britain saved billions by essentially leasing its nuclear deterrent from the US. The cost of independent development and maintenance could quickly become prohibitive. What is more, he said, the British government welcomed the chance to revamp the country's submarine-construction capacity that renewing the Trident system would provide.

It can be countered, of course, that Britain does not face an all-or-nothing choice between essentially leasing from the United States or going it alone. Why should the prospect of closer co-operation with France, as recommended in the last defence Green Paper, not include sharing a nuclear deterrent? (Miller answers this by hinting that if the US wouldn't trust its defence to France – which it wouldn't – then why, by extension, would Britain? He also plays down the value to the US of a loyal, nuclear-capable ally on the other side of the Atlantic.)

It is also true that a whole separate category of arguments can be marshalled in favour of neither renewing Trident nor retaining a nuclear capability at all. In so doing, we would set an example to others, accept a diplomatic and defence profile more appropriate to our economic means, and reduce the risk of exposing ourselves to nuclear retaliation. But if Britain is, as it seems, intent on retaining its status as a nuclear power, then the vulnerability argument in all its aspects has to be addressed. And if it is, then the choice may boil down to the renewal of Trident on the current terms, or dispensing with a nuclear deterrent altogether. Maybe that superficially attractive compromise just doesn't exist.

m.dejevsky@independent.co.uk