Retro Puzzle (Norwood 1995)

What were the last eight moves?

It's a nice retro problem but the first move is a cheat as it is not fully defined.

Btw, here is an old version of mine of a very similar puzzle. You can unambiguously retract the last 16 single moves (apart from repetitions). Obviously the position is less elegant than Norwood's. All things come at a price

I liked that puzzle - thanks - but I managed to get it back 18 moves to the position below so must have made a mistake I guess?

Yep, you did. The move 2.Ng5 looks unique because the interface uses short forward notation when possible. But in fact the knight could have come from either e6 or e4. It doesn't matter that the knight covers f8 because bK came from f8 or g8 escaping from check! Which invalidates the first move as well. So it stays at 16 I guess!

Don't know about 8 moves, but I can go back 8 ply, if that's what you meant.

8 Moves in this context mostly refers to 8 single moves. For some reason, ply is more often associated with computer moves. BTW, my diagram retracts 8 full moves