Well, I wouldn't have chanced it given how inconsistent they can be. If I travelled before the station opened and, given you can't get excesses for anything on a TVM, I'd have had no choice but to buy a new ticket.
And it's odd to be told to write the date on the back and under no circumstances to try and re-write the date on the front (as it will look like it has been tampered with) and then see the thread about someone having been told off for doing it.
Clearly you would need to have tried to write on the date - and if the ink didn't flow THEN you write the date on the back and leave the front alone. Leaving it totally empty is not what he meant or suggested.
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Bloody hell - they've changed the carnet tickets again!
They're no longer marked Out and Rtn - but just sold as singles. I asked for my usual carnet pack and simply got 5 x Hatfield>London singles and 5 x London>Hatfield singles - priced at £25 each and printed in two separate batches.
As I'd got out of sync on account of having to buy a new anytime single to go in the peak, I guess I could in theory buy more of one ticket than another.. but there must surely be a minimum amount you can buy if there's a discount.
I am not even sure what the discount is anymore! If only they didn't have an expiry date (or more than 3 months), I'd consider buying a handful of peak rate tickets too - just in case.
I wonder when First will change them again!