Stations that are closed/closing/having work done

These stations were already long enough for 3 car trains:
Bank
Canary Wharf
Heron Quays
Island Gardens
Langdon Park
Stratford
Canning Town - King George V

This station has been extended:
Poplar

These stations are having work done:
Tower Gateway (station closed until Spring 2009)
Shadwell
West India Quay (Platform 1 has closed because of the Delta Junction upgrade)
Crossharbour
Mudchute (Being rebuilt with a third platform)
Greenwich - Lewisham
Bow Church
Devons Road
(Limehouse and Westferry are also having work done, but it doesn't look like it has anything to do with the platform extensions)

These stations will not be extended:
South Quay (will be replaced with a new station)
Cutty Sark (selective door opening will be used at this station)

How come Bank is already long enough? I mean, it was opened in 1992 - but two subsequent extensions (Beckton and Lewisham) aren't long enough.

Cutty Sark is especially strange, because I think Island Gardens is also underground and built at the same time - but it is longer.

Cutty Sark was very nearly not built because of planning concerns - it sits in the heart of a conservation area. There were a lot of complaints about the building demolition required to construct it, and what would be put on the site around the station (a bit like the Camden Town débâcle). I seem to recall that this caused the platforms to be shorter than would otherwise have been liked.

I'm fairly certain that for Bank it just made sense to build longer platforms in one go, as the cost of extending later would have been substantially more. Nice to see some forward planning for once.

I think the works at Bank are to upgrade the signalling and to make that compatible with three-car trains rather than to do anything to the platforms.

All the information you need is on the DLR website.
developments.dlr.co.uk/enhancements/capacity/overview.asp