Political party conferences lost their real purpose years ago. In the old days (by which I mean the 1980s) committed members would gather to debate policy. They would discuss the big issues of the day, vote and set the direction of the party.

The process gradually withered as parties became more professional. Conferences became rallies, conduits for the messages the leadership wanted see in the papers or on the nine o'clock news (it was at 9pm in the 1980s). Rows, splits and embarrassing defeats were banished.

The new world of slick, presentational party politics, which everyone thought had been perfected by Tony Blair's New Labour until the modern SNP came along, is surely here to stay.

But last weekend Scottish Labour provided a reminder of how healthy and, whisper it, exciting politics can be when the grassroots is given its voice.

The occasion, of course, was the party's vote on Trident, specifically on whether it should support or oppose the replacement of Britain's nuclear deterrent when the decision comes up at Westminster in a few months' time.

Not since the SNP debated, and reversed, its opposition to Nato in 2012 have so many political journalists left the Press room to witness a conference debate.

The verdict from delegates was positive.

"We've nothing to fear from open democratic debate. We are stronger when we do it and weaker when we don't," said Neil Findlay, a staunch opponent of Trident renewal, who was at pains to praise Scottish party leader Kezia Dugdale for creating space for the debate as part of her promise to "re-democratise" conference.

His comments were echoed by conference chairman Jamie Glackin, who wrapped up the 75-minute debate with the words: "It's great to have passion back in debate at a Labour conference."

There are lots of reasons why Ms Dugdale might have fought shy of encouraging the debate.

The overwhelming decision to oppose Trident renewal - the motion was carried by 70 per cent of the party - certainly lands her with some real difficulties.

For a start, as a supporter of multilateral nuclear disarmament, she finds herself leading a party whose agreed policy on a major defence issue she rejects, just as anti-Trident Jeremy Corbyn is at odds with UK Labour, which remains committed to supporting renewal.

And, as it is now party policy, Scottish Labour is expected to set out its position on Trident in its manifesto for next May's Holyrood election.

But that will raise questions about what it actually means. Will Scottish Labour's opposition actually count for anything if UK Labour continues to support Trident when its lengthy defence review produces a policy for the 2020 General Election?

Labour will continue to be attacked as "divided and in disarray" even if the decision does encourage a few voters to follow the conference slogan and "take a fresh look" at the party.

But holding the debate has been good for Ms Dugdale. For all Scottish Labour's many problems, she can count her first conference as leader something of a success.