Happy 50th birthday, PMQs

It often ends up a childish, squabbling mess. But I wouldn't change PMQs for the world.

There are two observations which every first-time visitor to prime minister's questions always makes. These are: "It's much smaller in here than you'd think, isn't it?" And: "It's much louder in here than you'd think, isn't it?"

No coincidence, really. The Commons chamber is a small, confined space. It feels even more crowded when there are 500 or so politicians, a species given to voicing their opinion, doing so at volume all at once. Those who can't squeeze on to the benches crouch on the steps, or gather behind the Speaker's chair, or opposite him at the bar of the House. They've all come for the same thing - political theatre, at its rawest.

Pity the poor warm-up acts who answer questions in the 30 minutes before the main event gets underway. Usually it's the minister for Scotland, or Wales, or the international development secretary, who has to try and make his voice heard over the growing clamour of conversation as the chamber fills. With five minutes to go, the Speaker invariably begs those present to keep their gossiping at a low volume. John Bercow, the current Speaker, has even come up with a new word for this - "chuntering" - which has become a very well-established part of parliamentary slang.

The leader of the opposition is waiting in his seat. He's eagerly confident to get started. His spin doctors have already written the script for him, based on whatever they think will wound the government the most. The prime minister usually hurries in with just a couple of minutes to go, clutching a bulging folder which contains quick reminders of the government line on every conceivable subject under the sun. He (with one very notable exception it has always been a 'he') tries to appear calm and collected as he leafs through his revision notes.

Finally, Big Ben bongs 12. "Questions to the prime minist-ah," Bercow declares. And so it begins.

What follows is nearly always electric stuff. It is by far the most gripping part of the parliamentary week. Sometimes we forget just how lucky we are to have this regular session as an established part of British politics. Imagine Vladimir Putin or Angela Merkel having to face their political enemies on a week by week basis. Imagine Nicolas Sarkozy licking his lips nervously, or even Barack Obama, as all their follies and weaknesses are pointed out to the nation. None of these leaders have to deal with this weekly trial.

The pressure is intense. The press of the nation are peering down from their gallery above at the bearpit below, pens poised in their hands. When the leader of the opposition stands up for the first of his six questions, the entire political world pays attention. The leader of the government is about to be held accountable for his actions, and all those under him. When there's a major issue testing his administration, there really is nowhere else to be.

Which is why so many people are disappointed with what comes next. All too often the promise of the spectacle does not get reflected in reality. Sometimes the opposition figurehead buckles under the pressure to deliver first, in which case the PM is able to emerge from their corner fighting tooth and nail. At other times the prime minister successfully deploys the many evasive strategems which have developed in recent years - the barrage of statistics, the question turned on its head, sometimes even the smokescreen of pure waffle - to wriggle out of a tight spot. All too often, the net result is the same. Like a collapsing rugby scrum, the intensity leads to nothing more than an ugly mess.

"The public don't like it," Speaker Bercow has taken to reminding MPs when the highly-charged Commons reverts to type. Yes, MPs appear childish in the heat of the moment. They yell across the divide. They jeer. All too often, they appear most infantile just at the moment when everybody is paying attention. No wonder they have the reputation they do.

Yet, oddly, it's not their fault. Winston Churchill thought this was what you had to expect when the parliamentary chamber was devised. There's a reason the two sides of the chamber are two swords' lengths apart. "First we shape our buildings, Churchill said, "and afterwards they shape us." British politics, with its government and opposition benches, is inherently divided.

If you want to take some of the spice out of parliamentary life, the best way to do it might be to reshape the Commons chamber. Some sort of horseshoe arrangement might be worth considering, perhaps. This is the new age of coalition politics, after all.

Personally, I don't want that. I like that sense of anticipation as noon on a Wednesday approaches. I relish the chance to see the prime minister made to face the consequences of his actions. Not at a general election several years down the track, but right now, this week, in front of the country's elected representatives, live on television.

It may collapse into squabbling more often than it should. But when that potent cocktail of confrontation gets mixed just right, when the two antagonists are on their game, the results are simply unbeatable. The public want to see passion from their politicians, don't they? So long as it's not the Silvio Berlusconi kind, they get what they're looking for here.

That's why I wish PMQs a very happy 50th birthday. Here's hoping it lasts just as long again.