On Tue, 24 Apr 2007 22:12:15 +0100, Dave Newt wrote:

A followup question to this if I may (and if you're still watching):

1) Presumably if these allow unlimited London-Hertford journeys each
day, I presume it would cost exactly the same if the person lived in
London and worked in Hertford, i.e. same ticket and same price?

Yes. (Although a Standard Day Return from London to Hertford is
cheaper than one from Hertford to London.)

2) Assuming the answer to (1) is yes, could it be bought on Oyster at
the London end?

I've never seen this advertised, but Paul C informed us in a
recent(ish) post that the answer is yes - you should be able to buy
one at any LU ticket office.