The East London Line is basically a north-south route, except for the
upcoming section to Highbury and Islington. But what if a connection
were made to the Lea Valley Lines, which according to my calculations
(which are sometimes wrong!) are only three-quarters of a mile away
from Dalston Junction)? I'm not sure whether this would be best on the
surface, elevated or underground, but then you could have West Croydon
and Crystal Palace trains to Enfield Town and Chingford...

Sorry just daydreaming again!