Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Thermostat turned to maximum
Connect a U-gauge to the Burner Gas Pressure Test Point
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the boiler to execute its ignition sequence and the burner to ignite.
Is the burner pressure approximately 13.6mb?
When gauge is removed pressure test point should be tightened and checked for gas tightness.
Note:
This boiler has a "soft light" mechanism on the gas valve to help prevent hard ignition. This means on normal operation it should ignite at 4mb and slowly increase to operating pressure over approximately 6 seconds.