Boltar wrote:

Charles Ellson wrote:
.. and would also make it difficult for any kind of mixed running on
or off the DLR which might occur in the future.

I can't see that ever happening. I doubt much if any standard mainline
stock
would be able to negotiate the sharp bends or steep inclines on the DLR
and the DLR stock uses a unique (in britain) 3rd rail system so it
couldn't run
under its own power anywhere else unless modified. And then theres the
good old HSE to factor in with mixed running rules etc....

I think the OP was thinking more in terms of DLR trains running on
Network Rail lines rather than vice versa (though you're probably still
right about the HSE). Of course if/when the Stratford International
extension happens, the DLR will be taking over Network Rail standard
infrastructure (i.e. the end of the North London Line) and converting
the electrical system from standard 3rd rail to side-contact.