A slow creaking at first. Then definite movement. And eventually, finally, the government's forestry policy comes crashing down.
The rumours of last Tuesday's Cabinet meeting have been whispering like autumn leaves through the Westminster jungle these last eight days or so. "The question is not whether they're going to U-turn," one Conservative backbencher told me excitedly, "but how they're going to do it". From little acorns big U-turns do grow. This one was a political hurricane that nearly brought the House down. MPs have received hundreds of emails on this issue, more than any other in many cases. The opposition have done their gardening job well, carefully cultivating that grassroots opposition and trying to fertilise dissent on the government's benches. You might even say they were seeking to splinter the coalition.
So it was no surprise that Ed Miliband used three of his questions at this week's session with David Cameron on the issue. The prime minister, having initially adeptly dodged Miliband's insipid attacks on the economy, was put in a rather more unfortunate position. His attempt to avoid the issue was desperate. "It is a consultation that we put forward," he explained. Its purpose, Cameron argued, was to listen to people's views and to amend them if needed. "What's so complicated about that?"
This, as everyone in Westminster knows, is complete nonsense. Consultations are there to make it appear as if the government is listening. Or, more charitably, to at least ensure they are not going to lose a general election when they do what they always planned to. The problem is, the uproar at the proposals to privatise the Forestry Commission has actually made ministers think again. Cameron all but acknowledged that today. But he did so by laughing, shrugging, jovially blustering his way through, so that you almost didn't notice it happening.
It's a slow process this, isn't it? The only way to really appreciate the movement of Earth's beautiful flora is to use time-lapse photography. Just ask David Attenborough. That excellent naturalist was able to show the twisting, writhing growth and movements of plants only by speeding them up.
He would be a good choice for consultant on a programme about the government's U-turns. They happen so slowly that at any one given time - during a Wednesday lunchtime prime minister's questions, say - it might appear as if the government's position was still, unmoving, and therefore respectable. How wrong that is!
"Even he must appreciate the irony," Miliband scoffed. The trees are being sold off by "the guy who made the tree the symbol of the Conservative party".
There's something awkward about the way Miliband and Cameron interact at PMQs. Without the clear clunking blundering of Gordon Brown, Cameron seems somewhat disarmed by Miliband's limpid attacks. Their oneliners are stilted, unnatural, somehow lacking bite. "Everybody knows he's going to have to drop this ludicrous policy," Miliband said, in one of his best lines. Cameron's response was a little confusing. "I think the bandwagon has just hit a tree." There wasn't much laughter then. These exchanges almost seem - well - wooden.
If anything has come to a juddering, unexpected halt, it is the government's commitment to selling off the forests. Where Cameron was bullish and firm last week, he is wavering, teetering even, seven days later. If you haven't seen it before, this is what mid-topple looks like. Timberrr!