Barry Salter wrote:

I think I'm right in saying that *all* of the ELL stations have a
useable length of 4 cars, even the relatively "new" Canada Water. And
most of the North London Line stations are limited to 3 cars at
present...

Cheers,

Barry

Not quite.

Whitechapel, Shadwell, Surrey Quays and New Cross Gate can all take
eight-car trains - they all have pieces of platform that are out of use
at the moment and can be easily brought back into use.