"Tom Anderson" wrote in message
...
This is not an authoritative answer, but i did finally notice
that according to Quail, they do cross, and the crossing is
indeed a little way south of Harringay Green Lanes; probably
too far to build a station with interchange, though.

I'd always assumed they cross somewhere between Manor House station and
Woodberry Grove, where there are shafts down to both lines. Woodberry Grove
is quite a way north of Harringay Green Lanes, IIRC.