What one big idea should Labour come up with before the next general election? There are a number of candidates, some of which are bursting out of their chrysalis as we watch – the prime minister’s relatively brief but policy dense statement on constitutional reform on the 10 June is a big one idea plus – and the clear import of the statement is that we will be moving on many aspects of the package in months rather than the more traditional years or even decades.

Big ideas in government usually take big amounts of time to progress from idea to proposal to detail to implementation – very often via a substantial dose of civil service advice that to proceed would be ‘brave’ and that it would be safer to have a long period of consultation; perhaps a commission of enquiry, minister. The strong sense of ‘carpe diem’ about the constitutional proposals shows that we can galvanise ourselves to vault over this process of entropy, and perhaps points to at least something good coming out of the recent difficulties.

So in that spirit here’s another ‘big idea’, or rather, another big process that we can get seriously under way in a very few months.

In September, the ministry of defence will have to review progress on commissioning for Trident’s replacement and take further decisions to commit spending. The original 2007 decision to go ahead with the replacement has long term cost and development implications, and of course very substantial commitments on long term spending – perhaps £60bn over thirty years or so, if we count the build cost (£20bn) and the annual maintenance and refitting cost over the projected life of the new submarines. This commitment is at least ‘earmarked’ in future spending plans, and what we might do in September, therefore, is to start to cement these commitments into place. The arguments for a full scale rolls royce replacement of Trident, a dinosaur system that was designed for response in an era of superpower mutually assured destruction (MAD), seemed fairly thin then, and in an era where we will need every pound we can find to maintain public services, thinner still now. The decision then though was swayed by a key line of argument – we have, historically concentrated our nuclear deterrent down to submarine launch only, and therefore we have to invest in a new submarine platform, since (counter-intuitively) that would be cheaper, probably than re-inventing long abandoned alternative platforms. The choice was, it was argued, Trident or a unilateralist position of dumping UK nuclear weapons.

But this is not so in reality. Right now, we are building a new class of nuclear powered submarines – the Astute class. The choice now is whether we commission a larger or smaller fleet – seven or eight as against four. These submarines can be equipped with long-range cruise missiles equipped with nuclear warheads. True they would not exactly be son-of Trident ICBMs able to obliterate most of Russia several times over – but that is not where future deterrence will lie. We are entering an age when the perception of minimum intervention replaces that of cold war MAD. Frankly, an expanded Astute class fleet able to deliver minimum deterrence pretty much anywhere fits future defence patterns far better than the museum pieces that son of trident are already becoming long before they will be operational. Building and equipping an Astute based platform would be perhaps a third of the expense of the Trident programme: a more appropriate deterrent at a third the cost!

The big idea has a part two: why not now announce the biggest piece of hypothecation out – announce that we will allocate the difference in forward measures to combat climate change, and particularly to invest in the energy and low carbon energy production efficiency measures that we know we are going to have to do if we are to make substantial progress on our climate change targets by 2020. Eleven years of spending billions on a system from the 1950s; or eleven years of spending the same amount of money on investing for 2050. Not a hard choice to make, I wouldn’t have thought: and we could start it all off with a statement on a Wednesday afternoon in October…