On the back on my thumb, in one of the creases of skin that line the knuckle, there is an ink spot. Bend the thumb forward and the ink spot is visible. Hitch a ride somewhere, by which I mean close the fingers in to a fist and arch the thumb back, and the ink spot disappears in to a furrow of flesh. As the lips of the wrinkle purse together in a thin dark line the colour of the skin also changes, from ruddy nude to sallow cream. This distracts the eye and camouflages the ink. The spot vanishes.