Indesit WG1030 won't do final spin?

From time to time my Indesit WG1030 refused to do the final spin (stage 7), although the rest of the cycle seemed to be all right; for example, the drum turned and spun during the wash and rinse cycles.

It now won't do the final spin at all. It drains, and we've checked that there is no obstruction to drainage, but the drum just sits there. The timer knob continues to the end of the cycle, but there's no spin.