Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Remove Test Point Screw (under boiler
adjacent to Gas service tap)
Attach pressure gauge
Gas On

Observation:

Observe pressure, if satisfactory turn off gas remove pressure gauge and replace test point screw.
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.