"Trident Tested" answers only one small part of the issue. Its conclusions are:

• There are foreseeable risks which a nuclear deterrent is likely to reduce; and
• The best value in deterrents is submarine based.

These conclusions are only useful if they are taken in the context our overall strategic options for reducing risk from agression by other countries. These broad options are three:

1. The pacifist option of unilateral disarmament.
2. Reliance on collective security.
3. Armament under our independent control.

As a pacifist, I would prefer the first. But there is simply no chance of it working unless we disarm completely and are evidently prepared for foreign invasion should that happen. Simply abandonning one weapon unilaterally, nuclear or other, would leave us with just a weakened committment to some mixture of the other two options. It is evidently a choice which has poorer likely outcomes than continuing with the weapon in question.

If our principal option is to plump for collective security, then the likely outcomes are better the more succcessful is the collective effort to reduce and eliminate the threats from weapons of mass destruction. In that context the logical move is to continue with a nuclear deterrent, and to place it formally and very clearly on the bargaining table. Britain would have a permanent and prominent posture that at any time we would be willing to abandon our deterrent for worthwhile progress in eliminating weapons of mass destruction in other nations' hands.

If the British government's preferred stance is armament under our independent control, the question reduces to one of cost-effectiveness -  "Will a Trident repalcement deliver a greater liklihood of risk reduction than other defence spending?" That seems to be a question that our armed forces are willing to debate, but which our Government shies away from.

A policy of developing a Trident replacement that is always on the table as something we are willing (and eager) to forego for greater collective security makes sense. The case for it as part of a set of weaponry designed to allow us to stand alone should we need to simply has not been tested.