An interesting question for me is what was the purpose of all these varying shapes? If it was simply to cancel the ticket to prevent reuse then why the hassle?
Would anyone ever be clued up on all these clips/stamps to detect an irregularity?
I was once (early 1980s) frog-marched into the station inspector's office at Paddington, while trying to board an evening train back to Great Malvern.
The tickets at that time were the long ones with a printed destination and a machine-punched origin from the starting station, one ticket sufficing for the return trip.
I used to travel Great Malvern-Slough in the morning, (break of journey), Slough-Paddington over lunchtime (break of journey), returning from Paddington late afternoon.
All perfectly valid on the Great Malvern-Paddington return tickets of the day (would be Anytime today, I think).
But resuming the outward journey at Slough one day, the guy on the gate nipped the ticket with an edge triangle, and later at Paddington, starting the return journey, they decided I was a fraudulent traveller as the ticket had been "previously used".
It turns out the edge triangle indicated I hd already started the return journey, not resuming an outward one after a break of journey.
We parted more of less as friends, although I'm pretty sure they still thought I was being devious and was being "let off" lightly.
I have never knowingly defrauded a rail company over 60-odd years of travel, and have missed out on decades of non-existent BR delay-repay for disrupted journeys.
They were the days when a gang of burly ticket inspectors in full regalia would board every eastbound intercity train at Reading and work though the train before Paddington.
I think their descendants probably work the ramps at Euston today...