In message , at 01:04:45 on Thu,
29 Sep 2011, Theo Markettos
remarked:
I'd like to travel from Finsbury Park to Shelford (Cambridgeshire).
There are two obvious routes: (1) train to Cambridge and then train to
Shelford; (2) Tube to Tottenham Hale and then train to Shelford.

There's another one that's only slightly fruitcake:
Finsbury Park to Hertford North
walk to Hertford East
Hertford East to Broxbourne
Broxbourne to Shelford

I wonder what the routing would make of that?

It depends on whether you are allowed to walk between Hertford North and
East.

The [only] map which applies to this journey is WA.

If the Hertford's comprised a Routing Point Group Station[1] that would
allow walking between them[2].

They aren't marked as a Non-Routing-Point Interchange (which appears in
the key of recent maps), which I presume would allow walking, but
neither is *anywhere* else, nor is that term evident anywhere else in
the literature.

So it's impossible to say that it's definitely allowed, but it could be
allowed and yet not obviously so from the literature.

[1] Glasgow is a good example of one of those (with a walk between
Central and Queen St figuring in many journeys). nb Despite being marked
as one on map WA, Broxbourne isn't in the list of such groups (whereas
Stansted and Tottenham Hale are).

[2] Plus there are special rules about cross-London trips, that I won't
go into here.
--
Roland Perry