Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Disconnect ignition lead and earth lead from top of spark generator
Fit crocodile clip to spark generator as shown in the picture by
wedging it in the gap next to the earth connection
check it is fitted securely
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow boiler to complete 3 minute self check.
Shortly after the fan starts to run can a strong consistent
spark be seen at the top of the spark generator?
Note:
Appliance should spark for approximately 5 seconds on each attempt at ignition.
There may be a very brief (approx 1/4 second) pause in sparking halfway through each attempt.