Set Appliance State:

Mains Power Off
Boiler Thermal Store must NOT be at maximum temperature.
Models with Programmer: Rocker Switch to Continuous.
Models without Programmer: Rocker Switch to ON.
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

After a few seconds (purge period), the boiler will light, as indicated by the Green Neon illuminated on the front panel.
Does the Green Neon stay illuminated for a period in excess of 20 seconds?