Alan Moore claims to have met his creation on two occasions. In 1993, he told Wizard Magazine:

One day, I was in Westminster in London — this was after we had introduced the character — and I was sitting in a sandwich bar. All of a sudden, up the stairs came John Constantine. He was wearing the trenchcoat, a short cut — he looked — no, he didn’t even look exactly like Sting. He looked exactly like John Constantine. He looked at me, stared me straight in the eyes, smiled, nodded almost conspiratorially and then just walked off around the corner to the other part of the snack bar.

I sat there and thought, should I go around that corner and see if he is really there, or should I just eat my sandwich and leave? I opted for the latter; I thought it was the safest. I’m not making any claims to anything. I’m just saying that it happened. Strange little story.

His second meeting with his creation was illustrated in 2001’s Snakes and Ladders, an adaptation by Eddie Campbell of one of Moore’s performance art pieces:

Years later, in another place, he steps out of the dark and speaks to me. He whispers: ‘I’ll tell you the ultimate secret of magic. Any cunt could do it.’