On 6 Apr, 14:25, Tom Anderson wrote:
However, you'd only need to add one crossover between the Canonbury
and Moorgate lines south of the station to let Canonbury trains reach the
track between platforms 4 and 5, from where there would be cross-platform
interchange to platform 3, which is the down fast, where there are ECML
trains coming out of KX.

Only a few trains use platform 3. Most are routed into 4/5.

It's also worth mentioning that the Network Rail business plan
includes bringing platform 0 back into use so Hertford-Moorgate trains
are segregated all the way from Alexandra Palace. That would make 7
the most likely option if this ever happened.

(there was also a long term suggestion in the ECML RUS to run inner-
suburbans to Canonbury and beyond once Moorgate is saturated, though
with no discussion of the NLL's capacity issues)

U