The mood at Labour's conference this week was buoyant. But Birmingham MP Sion Simon reports that delegates were also in something approaching a state of shock.

It has begun to sunk in that they could win another election - and, as he confidently predicted, they could win it with an increased majority. It remains to be seen whether that one comes true, but it's certainly not impossible.

Since Tony Blair resigned, it has become clear that a fair bit of the public's hostility towards the Government was really directed against Mr Blair personally. Now that he's safely out of the way, people are willing to give the Government a chance again.

Gordon Brown, in his new role as party leader, has apparently learned to smile. Labour has even placated critics of the Iraq war by quietly admitting that the invasion might have been a bit of a mistake and George Bush does have his faults.

Meanwhile, the Conservatives helpfully began to implode just as they faced their biggest challenge since David Cameron became leader. Mr Cameron's team had believed Tony Blair was a political asset for Labour, while moderate voters would be repulsed by Gordon.

When this turned out to be wrong, one or two Conservative backbenchers and prominent supporters responded by turning against their own leader. Who knows what they were thinking.

So Labour is now beginning to believe that it could win the next election - not by the skin of its teeth, but in a big way.

This would devastate the Tories. It would send the message that the Cameron experiment had failed, and all this modernising, touchy-feely stuff was for the birds.

Mr Cameron could probably survive losing an election as long as the Tories made some progress, winning some key seats and cutting Gordon Brown's majority.

But if they lose badly, he'll be out. And this would be a disaster for the Tories, as David Cameron is right - they need to change, and to embrace modern Britain.

Neil Kinnock told a fringe meeting at the Bournemouth conference this week that he hoped Gordon would "grind the bastards into dust".

He may get his wish. But then again, the Tories have their own conference next week, and may receive a lift from that.

Because there is a lesson from the ascent of Gordon that Mr Simon and his colleagues shouldn't forget. Remember how the Conservatives were riding the crest of a wave and Labour were slowly sinking? Just a few months ago? Remember how it changed very quickly?

As the shellshocked Tories heading for Blackpool this weekend can testify, in politics you should never count your chickens before they've hatched.

The reality is that Gordon Brown has not yet been tested.

He faced some difficult issues in his first months as Prime Minister - terrorism, floods and so on - and responded in a calm and dignified way. Naturally, voters liked this.

But that's not what being Prime Minister is all about. Most days do not bring a crisis.

What Mr Brown will really be judged on is whether he can improve our schools, improve our hospitals and bring down crime.

He has been Prime Minister for around three months -and Parliament has been in recess for almost all of that period.

But MPs return to Westminster next week and Mr Brown will then be expected to get on with the mundane job of governing the country.

Will voters believe he is improving standards in their child's classroom, or making their local hospital cleaner?

Or will they conclude that they have heard it all from Labour before, and consider the merits of putting someone new in charge?

It's impossible to predict, but the events of the past three months don't provide much guidance. Mr Brown has still not really got stuck into his new job.