What it means
Used when someone seems to have gone a bit mad or started acting wildly irrational, like their brain took a funny little detour and never quite came back. It can be said with a grin, but also with a proper eye-roll when someone’s talking rubbish or making daft choices. Very British, a bit old-school, and still well alive.
Usage examples
"She’s gone round the bend, mate. Bought a £300 air fryer, banned carbs, and now she’s training for five marathons in five days down the rec with a Lucozade"
"These endless forms are driving me round the bend, I can't take much more."
"You’re seriously gonna remortgage the house for a hot tub and a garden bar? You’ve gone round the bend."
"Mum’s gone round the bend since she found that Facebook marketplace page. There’s a ceramic duck in every room now."
"He wants to quit his job, buy a narrowboat, and start selling candles on Instagram. Man's gone round the bend."
Where it comes from
The bend may be a curve of road or river, but the likeliest root is the asylum: certain Victorian institutions sat at the end of a long bent, curving drive, kept well out of sight. To be sent round the bend was to be carted off there, and so to have lost your marbles.
