I recently got a p*nct*re in a Marathon.
Close inspection revealed a doubly snapped off thin thorn,
just on the shoulder where the thick anti-puncture layer isn't,
but the tyre is still a few mms thick.
Just thick enough to hide enough thorn to get to the inner tube when the tyre was at the correct/worst orientation.
Had to use needle nose pliers to remove the thorn stub.
I recently got a p*nct*re in a Marathon.
Close inspection revealed a doubly snapped off thin thorn,
just on the shoulder where the thick anti-puncture layer isn't,
but the tyre is still a few mms thick.
Just thick enough to hide enough thorn to get to the inner tube when the tyre was at the correct/worst orientation.
Had to use needle nose pliers to remove the thorn stub.