Tom Sutcliffe: Clegg grows into a man with the confidence to interrupt first

As Nick Clegg found out last week, 90 minutes is a long time in politics. And as everyone at home found out this week, it can feel like a very long time on television, too. In prospect the second of the leaders' debates had been infinitely more enticing than the first.

Yes, the novelty might have diminished but then so had any cynicism about the effect these encounters might have on the political climate. Sky News weren't just broadcasting it in High Definition. It was going to be scrutinised in high definition too – with a far keener sense of the importance of each performance.

In practice, despite that, it was impossible not to feel that an hour and a half may be more ground-breaking political excitement than the ordinary punter can take. In an accidental breach of the ban on mordant reaction shots, a wide angle of the audience caught a man failing to stifle a yawn at around the 60-minute mark – and I suspect he gaped for quite a few viewers at home. An hour would be ample.

Sky had built up to it as if it was a Moon launch. "One minute to go and counting," said Kay Burley, as the SkyCopter hovered over the Bristol location. And it was pretty soon clear that no one had failed to launch. They were all better this time round – even the set, which looked like the fragments of an ash-downed British Airways jet. Gordon Brown seems to have lost the fear of failure – perhaps because he's accepted the inevitable – and came out markedly more relaxed than last week. "If it's all about style and PR, count me out," he said. If it's all about a good make-up job and a better haircut, though, count him in.

Cameron too was crisper and more forceful, using his opening statement to try to lever open one of Clegg's weak points. But Clegg had grown the most – not a cat standing disdainfully on the sidelines of a dogfight any more but a figure with the confidence to interrupt first.

In the queue to disagree, Clegg was rarely second – and he showed no sign of deferring to either of his opponents. He was prepared to go below the belt with Cameron too, answering a point about the European Union by pointing out that Conservative MEPs had voted against a joint police operation to arrest continental paedophiles. Vote Cameron if you want your kiddies to be fiddled with.

Most of the cheesy anecdotes and worked up punchlines had disappeared. And Brown wasn't agreeing with Nick anymore. He was imitating him though, wheeling out a pre-prepared line at a point when Clegg was bickering with Cameron. "You know who these two guys remind me of?" he chuckled confidentially at the audience. "My two boys squabbling at bath time." It was second-hand and calculated and it didn't convince. He had another bad moment too when the small voice at the back of his mind screamed "smile", unfortunately choosing a moment when he was halfway through a sentence about the traumas of child abuse.

Clegg's worst moment came after Adam Boulton – frustrated by a role that is little more than a glorified traffic policeman – opened out a question on public trust in politicians by turning to the Liberal Democrat leader: "You're on the front page of The Daily Telegraph today," he said mischievously. Clegg shook it off briskly but the surprise of it briefly left him shaken too – for the only time in the evening.

And Cameron flared into genuine anger over Labour claims on Conservative plans for pensioners – an unrehearsed frustration which probably will have served him better than the synthetic intensity he deployed at several other points.

Unlike last week's debate there was nothing here to change the political map. But there was nothing, either, that was going to reverse last week's redrafting.