There's the aded interest in that I don't have to cycle across That London: Saarfend > Stratford >Highbury & Islington > Krapy Rubsnif > Huntingdon.
Wow - I hate to be the bearer of negative train vibes, but...
I've a strong
suspishion susspiss... idea that bikes are banned from the Moorgate to Finsbury Park line (i.e. the bit from Highbury to Finsbury Park) at all times. It's more a deep-level tube line than a bit of main-line railway, and all stations are accessed by escalator. Your best bet would be to bike that section, or bike from Highbury-n-Islington to Kings Cross.
[Goes off to fettle train-fu..]
Clicky for Map.As usual, it's ambiguous. Highbury & Islington is the last station in Zone C; "Cycles not permitted at any time on trains between stations in this zone" - but you're travelling away from H&I. But it's NOT shown as "in both zones". When one looks at the word-based restrictions
here, the very first one states:
However we are unable to carry non-folding bicycles:
At any time between Drayton Park and Moorgate.
So that pretty much rules out using H&I on the Moorgate branch. Sorry. You could ride H&I to Drayton Park, then take the bike on the train from there to Finsbury Park.
My preferred route from the North That-London Line is from Camden Town to St Pan (or KX), but it too involves carrying the bike down a very long flight (almost trans-Atlantic) of stairs.