Hi Adrian and
to the forum.
If the throttle had failed fully open
(or the cruise control had been activated by mistake) the brake switches should still have stopped the motor.
As the brake switches obviously did not cut the power, it sounds as if you may have a faulty ground connection somewhere between the main front harness multi-connector and the speed controller inside the hubmotor.
A faulty ground wire or connection would cause a full throttle signal at the controller. If the battery is connected in this state
(with a full throttle signal being supplied to the controller) a safety feature of the controller would prevent the motor from running again until a low throttle signal is first supplied, which is hopefully the reason why your motor no longer runs.
I suggest that you check that the 8 pin connector between the front harness and the motor harness does not have any damaged pins and that both halves of the connector are pushed fully together to hopefully avoid any poor connections.
If that doesn't make any difference, you can perform a simple test that bypasses the main front harness, brake switches, throttle and cruise controls and simply checks the motor, controller and battery circuit by disconnecting the main control harness and then bridging two throttle contacts with a piece of small diameter wire, I used a reshaped paper clip as indicated here:
Don't force the wire into the sockets as this can open the contacts up, resulting in a poor contact with the pins when the the main harness plug is refitted, you only need to touch it against the two contacts to hopefully make the throttle run at full speed, confirming that the motor, controller and battery are all OK.
Please note:
Because of the aforementioned safety feature, the power must be turned on before the wire is inserted into the correct sockets or the motor will not run!To avoid accidentally shorting out the wrong sockets, and causing possible damage, you can place a piece of masking tape
(or similar) over the other sockets to ensure the wire does not accidentally enter the wrong socket.
As it states on the diagram,
make sure the bike is secure with the wheel raised off the ground before you insert the wire and keep hands and loose wires etc. safely away from the wheel and tyre! If it doesn't run during the above test, the controller or motor harness could be faulty and may need replacing.
Please let us know what you find.
Alan 
