Below him the coach yard of the Central Post Office buzzed like an overturned hive. They'd got the turntable working really well now. The overnight coaches were arriving and the new Uberwald Flyer was gleaming in the lamplight. Everything was going right, which was, to the night-time climber, why everything was going wrong.

The climber thrust a brick key into soft mortar, shifted his weight, moved his foo—

Damn pigeon! It flew up in panic, his other foot slipped, his fingers lost their grip on the drainpipe, and when the world had stopped churning he was owing the postponement of his meeting with the distant cobbles to his hold on a brick key which was, let's face it, nothing more than a long flat nail with a t-piece grip.

And you can't bluff a wall, he thought. If you swing you mightget your hand and foot on the pipe, or the key might come out.

Oh… kay…

He had more keys and a small hammer. Could he knock one in without losing his grip on the other?

Above him the pigeon joined its colleagues on a higher ledge.

The climber thrust the nail into the mortar with as much force as he dared, pulled the hammer out of his pocket and, as the Flyer departed below with a clattering and jingling, hit the nail one massive blow.

It went in. He dropped the hammer, hoping the sound of its impact would be masked by the general bustle, and grabbed the new hold before the hammer had hit the ground.

Oh… kay. And now I am… stuck?

The pipe was less than three feet away. Fine. This would work. Move both hands on to the new hold, swing gently, get his left hand around the pipe, and he could drag himself across the gap. Then it would be just—

The pigeon was nervous. For pigeons, it's the ground state of being. It chose this point to lighten the load.

Oh… kay. Correction: two hands were now gripping the suddenly very slippery nail.