Worn out.

Parked the bike up this morning and thought to myself, what's that on the tyre?

Closer inspection revealed it was the canvas showing through the very worn tread! That's a good thing though as it means it's been used for what it was intended for. It doesn't owe me anything either as these Continental Gatorskin Hardshells last for ages and are very puncture resistant.

Best buy me another one.