There was very loud banging on the spin-up after the first rinse, but as it speeded up further this was OK. I left it to continue the cycle.
Later I came back to find all lights off, and was told that it had been making a loud banging noise. Door wouldn’t open when button pressed. Once I’d drained and opened the door manually I found the load still very wet (but not soapy) inside. The seriously unbalanced load was due to a hugely absorbent bathmat, washed for the first time.
I assume that a unbalanced spin had somehow killed the machine. What should I check?