Yet another non-spinning washing machine... lots of detail?

We have a Bosch Classixx combined washer/dryer that has stopped being able to agitate the clothes during the wash cycle, spin them before drying, or while tumble drying. When you switch it on, the dial moves slowly as usual, indicating that the programme *should* be progressing - but it isn't happening. It will not spin at any speed - 1200 or 600 rpm, or in any of the programmes.

The drum will turn freely by hand, either by rotating the drum itself or by turning the belt. The belt appears to be fine. The motor also turns when the drum turns.

My partner believes that the carbon brushes are fine and in good contact with the commutator. (He checked by looking inside with a torch). All of the wiring between the motor and the control board and timer is visually intact. He believes that the motor is fine because there is no visible sign or smell of any burning or "magic smoke escape". There is also no sign of any visible damage to the circuit board.

Apparently the next thing to check is "the circuit across the terminals on the motor, because there is a thermal overload switch inside which may have tripped", but he couldnt find that. Sites also suggest "checking" the voltage across the terminals with a voltmeter or multimeter, but they never say what the voltage should be! (Surely not 230V?).

What is most likely to be wrong?