Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Attach U-gauge to gas inlet pressure test point
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset boiler as necessary and allow the
appliance to complete its self check.
Observe the inlet pressure.
During the sparking stage of the ignition sequence there should be
a noticeable dip from standing to working pressure as the gas valve opens.
The Inlet pressure should also be at least N.G. 16.5mb / L.P.G. 28mb throughout the boiler ignition sequence and operation.
Note:
When pressure gauge is removed the test point should be tightened and checked for gas soundness.