My understanding is that the other individual has committed several felony crimes to write that check (various forms of banking fraud and theft), and given their signature to it as well, as evidence of both intent and proof of their identity. So it seems to me about as insecure as saying "I can't believe the sidewalks here are so insecure near roads, that a car could just drive down onto them and hit people." The idea is not to make it hard to move money around, but to instead make the punishment very high for trying to cheat the system.
Given the stated currency, I suspect the bank account in question is in the UK, so the criminal law wouldn't be entirely identical. But in any case, it wasn't necessarily a crime -- someone (especially if elderly or impaired) might have accidentally used the wrong chequebook. It's only a crime to write a cheque on someone else's account if you do it deliberately.
To me, the biggest issue here is simply "banks should not recycle account numbers".
I think this would happen more often with people with many accounts and many checkbooks accidently using the wrong book after closing an account, by accident.
