How can you trust the pounds nowadays with 1 in 3,333 being fake?
I think it's way, way higher than that figure for pound coins, something ridiculous like 1 in 40 or more. I certainly handle coins that feel dodgy on a near weekly basis.
As for forged notes I've never been caught out by one.
A mate of mine used to be paid exclusively in forged £20s. He said they were the best he'd ever seen. I thought they were total dogshit and if you didn't know just by looking, you definitely knew by touching them.
Every single cashier he handed them over to instantly knew they were crap but most don't care so they shoved it in the cash register anyway.