Purchased an e-ticket in advance via Trainline for my journey to a city (I live rurally). It wasn’t the orange type (the kind you activate) but the new ones with a QR code that are just white and add to your Apple Wallet.
The conductor said he’d never seen one before and wanted an orange ticket 
I said it was just as valid and even had to show him how I’d purchased it. He said they have no way of scanning a code and I needed a ticket.
Took some convincing and eventually he said all the technology went “over his head”. Not really his fault but AIBU that National Rail should be showing their conductors what a train ticket looks like 
Anyone else could’ve backed down and forked out for another and they aren’t cheap!