In message , at 23:22:46 on Sat, 25 Feb
2012, tim.... remarked:
The "only one journey" rule applies to the part outside the Travelcard
zones, once inside you can make as many journeys as you like (modulo the
possibility that even the semi-mythical +HS1 Travelcard might be invalid
from Stratford to StP.

No, I don't think so. HS1 is part of your inbound journey and can only be
travelled once.

If I have a Cambridge outboundary Travelcard, then I can travel back and
forth all day between (eg) Finsbury Park and Kings Cross. The "one-shot"
part is from Cambridge to Hadley Wood.

If it were true that using HS1 from Stratford to St Pancras isn't
allowed *at all* on a Travelcard (even a PLUS HIGH SPEED one), there's
no reason I can't get off at Stratford and travel back and forth by tube
all day.

But what may be the case is that the +HS1 Travelcard is valid for a
one-off trip to St Pancras, then as a Travelcard (excluding multiple use
on HS1),

Though one thing I don't know (and have been meaning to try for ages)
is, can I break my journey at Stratford (to visit the shopping
centre) and then continue later to StP (which would be my intended
destination whenever I buy super expensive ticket)?

If it's a CDR on HS1, then it should allow BoJ.

I know, but how do I prove that.

You ask to see the Fares Manual at a station, or ask someone to print
off the relevant screen from the Avantix CD.

BoJ is also allowed on the Travelcard, which gives them an interesting
problem at Stratford when you resume your inbound one-off trip on HS1.

http://www.perry.co.uk/images/ruleC4.jpg
--
Roland Perry