Someone once asked for a Carnet, which we don't do in my neck of the woods. I was determined to issue it, but didn't know how and I would never have guessed either.
The trouble with Carnets is that each TOC offering them has specific issuing instructions and conditions that apply.
For example:
- Chiltern offer 12 Anytime/Anytime Day Returns to/from London for the price of 10
- First Capital Connect offer both Anytime and Off-Peak Carnets, in multiples of five Single tickets, at a 10% discount
- Grand Central also offer both Anytime and Off-Peak Carnets, but in multiples of 10. These offer a 25% discount on the Off-Peak tickets, and bring the Anytime ones down to the Off-Peak price
- East Midlands Trains, meanwhile, offer packs of 5 or 10 Anytime Returns at a 10% discount, but only for "selected" journeys
- Gatwick Express, on the other hand, offer 10 Singles for the price of 8
- Heathrow Express give 12 Singles for the price of 9
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The Farringdon Und origin equates to London Thameslink in STAR. Zone U1256 is incorrect following the logic behind the zone system and there is no fare for Zone U1 - Elstree. London Thameslink - Elstree would be the correct pair to use at 6.80 SDS/13.30 SDR with no CDS/CDR fares showing.
Check the "London Area Ticketing" bit of iKB, specifically the bit about "Train-Tube-Train" fares (or whatever they're calling them this week).
As a "London Terminals" ticket isn't valid for journeys to/from/via Farringdon, Zone U1256 is the only origin that you could use, other than London Thameslink, as the journey passes through Zones 1-6.
In reality, of course, you'd only use Zone U1256 as the origin if it was the morning peak and the passenger needed tube travel. Off-Peak, even for a Single journey, you'd offer a Travelcard. For a purely point to point journey, on the other hand, you'd go for London Thameslink as the origin.