Having just cleaned the hob (soapy water galore) and put everything back, there is *one* burner which - despite there being a clear spark at the ignition pillar - just will not light.
Put a flame near it, and it catches instantly.
Have lit it, and let it burn for a few minutes in case something needed drying out, but it's still not working.
3 other burners and centre burner are perfect.What am I missing ?