"Part of the reason for this change was that notes, on average, lasted only nine months in general circulation, while coins could last forty years or more. The government also believed that the growing vending industry would benefit from the introduction of a one pound coin."

Maybe the economics have changed with polymer notes. But the BoE inflation calculator tells me that the £1 notes withdrawn (in 1984 money) would be worth about £3 today. So maybe the fiver is next.

Then there's the lunatics that want to abolish physical money altogether...

Something like that is already being discussed on the continent.

The memorial 5€ coin recently (which is legal tender) wasn’t just that, but it was also a test if a 5€ coin would be accepted, and doable.

There's been a British £5 coin since 1990 along the same lines (commemorative, but technically legal tender).

yay. Australians didn't die when they introduced the $1 note and remove 1c and 2c coins - they seem to do just fine.