Following a spot of cleaning of my gas hob, one of the four spark ignitors produces no spark. It's a plug in (from memory, as ICBA to delve into the cupboard to look for the lead last night) design and pushing any of the hob knobs (ooh, biscuits) should cause sparks at all burners.
Setting my multimeter to its highest (1kV) range, putting the probes on ignitor tip and ground suggets I'm getting voles to the ignitor tip but presumably not enough to jump the gap to make a spark. I've cleaned the outside of the ceramic insulator that goes up around the ignitor but still no spark.
What next?