Set Appliance State:

Mains Power Off
Gas On; Pilot On
CH Demand
Boiler Operating Switch in HW and CH position
Heating Control Thermostat (Potentiometer) adjusted to Maximum
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

The pump is situated behind the gas valve and secondary heat exchanger.
Operate the boiler in its CH mode allowing it to obtain a satisfactory operating temperature.
Remove the CH demand. Does the pump overrun?
Do not take sound or vibration as a sign of pump operation.
Note:
It may be necessary to reduce the heating load by turning off some radiators to reduce time taken for this test.