An addendum…
I’ve used the technique described further up the thread (One Day Travelcard on a Greater Anglia ITSO smartcard) successfully many times since my first trial last month. I’ve usually used Feltham-Waterloo and this gives me the required z1-6 Travelcard though I don’t go to either station.
Today I decided to start at Amersham or Chesham so purchased an Off-peak Day Travelcard with Amersham as the origin and Marylebone as the destination. The cost, as expected, was £10.10 (I have a Senior Railcard), and during the purchase process on GA’s app it says “Also valid for travel in London Fare Zones 7-9”. So this seemed to me to be effectively a z1-9 TC. Except it isn’t.
Only after purchase and loading to GA’s smartcard did I notice that the destination was London Zones 1-6 (0035). Ah, I thought, this isn’t a z1-9 TC; it’s a ticket from/to Amersham to the z6 boundary then it’s a z1-6 TC. The same result is obtained if you choose Brentwood as the origin.
To test this out, I started not at Amersham but Chesham. Sure enough, the POMs and the gateline refused to recognise the smartcard. I used my Oyster to travel from Chesham to Harrow-on-the-Hill where I had business anyway. I checked the smartcard at a POM at Harrow and the origin is given as AMSHAM, destination R1256, and route R40232. I then continued on my journeys around z1-6 using the GA smartcard with its z1-6 TC successfully.
I had hoped to do further tests on the way back to Amersham but a curious absence of Met trains to Amersham made that tricky so I had to settle for the hourly Chiltern train from Harrow to Amersham. All I was able to confirm was that the smartcard happily opened the gate at Amersham.
So the ticket is the same cost as a paper z1-9 TC and GA says the ticket is valid for travel in z7-9. This is true but, it seems to me, only on the direct route to Amersham. It’s no good for the diversions to Watford Met and Chesham and therefore may not be useful for the Tube Challenge.
Mike: thoughts?