Got it in one.

The external CCTV cameras with which we check the train before completing station duties are somewhat unreliable at the moment.

Most of the stations this wouldn't really be a massive issue at because there is a clear line of sight down the platform and drivers can operate the "local" door control panel and step out of the train onto the platform to check that the doors are closed correctly and that nothing is trapped etc.

Unfortunately there are a couple of platforms where the curvature prohibits this.

So a revised date of Monday (19/04/10) has been issued whilst Bombardier sort out the issue with the CCTV software, which I am told is the culprit.