Worst thing is, I'd actually handled it quite a few times, albeit not removed from the car. You know how tightly nested they are on the 4x4.
I'd looked inside it, cleaned it out, checked the electrodes, checked the phase, checked the rotor, unplugged and replugged the leads....
And the crack was just slightly obscured from the top by the end of the inlet, and the loom etc.
Was so sure it was in good nick I didn't even think about it.
Even when it was arcing out causing the miss and I recognised the sound, STILL didn't think cap. Coil? Leads? Plugs? Yep, all checked as possibles. Just feel a fool, especially after all the advice I've had off here!!
We Live and Learn.