In answer to scep. It shows a bright unmissable spot where the hole was,
I have never known a puncture it can't seal, which is why 'old bill' use it,
and the latest stuff cleans off the rim quite easily, I do tell the fitters it's in there though so they don't get a bootfull.
Last lot cost around £20 for both wheels, remove valve core, insert goo, refit/reinflate tyre, JD!
Great peace of mind when running for a ferry!