I noticed this snippet in the 2007 Network Rail Business Plan:
On the North London Line platforms are to be extended to allow 4 car operation.It's been suggested before in the Cross London Route Utilisation Strategy and various other places, but I'm fairly sure this is the first time it's been publicly discussed as anything more than a good idea. The timetable at the back mentions a date of 2010 for completion.
Oddly, the new trains ordered for the line will only be 3 car, and are due to be delivered by July 2009, which doesn't seem worth it if they're going to need extending straight away. Something else that doesn't add up is this from the TfL business plan:
256 new build vehicles in three-car and four-car formations. North London Railway (NLR) vehicles to be dual voltage, East London Railway (ELR) vehicles to be DC, with provision for future conversion to dual voltage use.All other public statements have said 152 cars total with the possibility of 200 more. Evidently they've ordered 104 more without telling anyone. Even more weirdly they still seem to be promising 6 car trains to the Olympics people (see page 80).