It's not my tyre either, luckily for me. I'm running on homemade tubeless conversion so I would've been showered with latex as well as having to repair and then replace the tyre...
It was on my mates bike, on a quick off-road excursion after work on Friday.
He was lucky, really, as he picked it up at the bottom of a pretty gnarly descent.
I was leading, and when I noticed he was no longer behind me, it was with a heavy heart that I backtracked to find him, expecting to discover him crumpled up on the floor but instead was treated to this most impressive puncture!