It was just like old times.

A real conference debate; real speeches; real passion; real argument. The SNP's debate on Nato membership was reminiscent of the great debates on unilateralism that took place in the Labour Party 20 years ago. Even down to the confusing motions and the card votes. All we lacked was Tony Benn and the union block vote.

In 1990 Labour abandoned unilateralism, by not abandoning it. The compromise, promoted by Martin O'Neill, the Labour spokesman with special responsibility for nuclear issues, was that Labour would remain unilateral in intent, but would use Britain's nuclear deterrent as a bargaining chip in future negotiations toward making the world nuclear free.

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It didn't quite happen that way, of course, and Labour has accepted nuclear weapons ever since. Unilateralists like Ken Livingstone and David Blunkett argued for a specified time limit by which nuclear weapons had to be removed. They were defeated.

So the advocates of unilateral nuclear disarmament in the SNP need to learn from history. They have secured a good vote and won a moral victory. The leadership had expected a majority of two to one, but in the end only squeaked it. Now those who wish to see the end of weapons of mass destruction must ensure that this decision to remain in Nato will not be finessed into a commitment to keep Trident on the Clyde more or less indefinitely.

While this was not a vote for nuclear weapons as such – neither was Labour's in 1990 – the vote allows Alex Salmond the freedom to use Trident as a bargaining chip in the independence negotiations that would follow a Yes vote in the 2014 referendum.

He might agree to keep Trident, perhaps, for 10 years in exchange for a bump in oil revenues, or some such concession. His party must ensure that this temporary stay of execution for Scotland's weapons of mass destruction doesn't become permanent.

But credit where it is due. This was an admirable debate and a sign that politics is still alive and well in the SNP. Salmond did not avoid the issue, but faced down his conference from the platform and gave his opponents a fair shout.

There is no need for this to lead to an acrimonious split in the party, though seeing Angus Robertson, the SNP defence spokesman, being roundly booed might be an indication that he has to mend fences with the party. Once party members start calling their leaders unprincipled hypocrites, it can become habit forming.

The victorious argument was simply that, to be taken seriously as a party of power, the SNP had to come to terms with Nato membership, even though it is a nuclear club. It has compromised its principles for the sake of political expediency.

The SNP has lost its innocence. It remains to be seen whether it gains power.