Thank you for all that have responded.
I'm not suggesting I would do such a thing but with an all-lines rover and the ability to plan many linked point-to-point journeys in a single day covering multiple tocs, I would have imagined the ability to evidence & claim against any delayed train would be open to abuse? How would the rover ticket track where you have been up to that point such that a delay can be claimed for?
Credit-card sized paper tickets (CCST) are inherently open to Delay Repay fraud, yes. It is usually impossible to verify whether the passenger has actually made (or intended to make) the journey they specify when claiming.
However, many ticket offices and retailers now issue multi-use tickets such as rovers and rangers in some kind of digital format - either in PRT (aka long "bog roll" tickets with a barcode) or sTicket format. These can of course easily be tracked, as any gateline or onboard scan is recorded in a database which TOCs can access when processing Delay Repay claims. Some journeys will go untracked because the passenger doesn't go through barriers and isn't checked onboard, but that will likely only apply to a minority of cases.
CCST fraud was historically reduced somewhat as many regional and intercity trains' guards would have "Zifa" ticket stampers, which could be configured so as to indelibly mark the train's headcode on the ticket. However these stampers haven't been issued for some years now, due to their cost and the reduction in the prevalence of paper tickets, and so are now very rare to come across.
Delay Repay fraud on CCST is one of several reasons why the industry is keen on removing CCST as a fulfilment option. Many retailers now charge extra if you choose ToD (collection at a ticket machine) and some don't offer it at all, or make the option less than obvious.
