I've stayed out of this as my views are well known, and in this company, heretical.
The basis of the Trident replacement decision is that it is a deterrent. This means it must be survivable and difficult to detect and track, and unless we are intending to go down the route of a strategic triad (which we're not, given the cost) then the only sensible thing - if a deterrent is needed - is a submarine based system large enough to ensure continuous-at-sea-deterrence (CASD). If there is a break in the continuous nature of it, then it's of limited value as a deterrent, especially if it is predictably not at sea.
Given this, a ballistic system is more likely to get through defences coming in at 15,000 mph (Mach 23) or so than a cruise system coming in at M0.9. More importantly, however, the flightpaths of ballistic and cruise missile are rather different, and therefore if your nuclear payload is only on a ballistic missile, then the country on the receiving end of cruise knows that they are not about to get nuked - which in those critical minutes could result in a different decision not to fire off nuclear missiles in response, especially if it's use it or lose it.
Given this, if the decision is that we need a deterrent then probably the correct choice is an SLBM, and buying Trident is going to be far cheaper than any other option - still massively expensive at £100bn over 25 years, but cheaper than developing our own.
So the question then is two-fold; do we need a deterrent? And should we afford it in tight financial times?
On the first, the issue is that for deterrence to work, it has to deter. So it means that:
- the people it is trying to deter need to be deterrable - and therefore rational.
- They also need to have territory - meaning that they have to be States.
- They have to be intent on attacking the UK and not be deterred by the threat of retaliation from allies (decoupling of the US nuclear umbrella)
The number of rational States that want to attack to the UK and believe in decoupling the US nuclear umbrella is vanishingly small. In fact, I can't think of any.
So on this basis, there is nobody to deter - and before someone goes off on Iran/North Korea etc etc, there is no evidence that they want to blackmail the UK. And as for rogue launches, they are inevitably non-deterrable, so it wouldn't matter if we had Trident or not.
If there is nobody to deter, then it does rather raise the question of why we're proposing to spend these vast amounts of cash on replacing Trident, especially when binning it within the framework of global nuclear arms reduction is sensible policy.
Can we afford it? Yes, but only at the cost of other capabilities. Should we? In my view, no. We should concentrate on using UK expertise to develop the verification regime to allow us to move towards nuclear zero.
I'm sure many of you will disagree, but it's time for the UK to have the debate on this.
S41