First there was a splinter on the side of the egg. A couple of hours later a small hole appeared as the chick used its egg tooth to batter away at its ovoid prison. An hour ago the hole was a little bigger and movement could be seen through the hole.
Then about five minutes ago the cheeping became much louder as the eggshell split in half and the chick emerged. The following video is a short documentation of a chick within a minute of its hatching.