One of the most enjoyable chess puzzles I have seen. I admit I only half-got it. I scratched my head for around 10 minutes and I gave up and played the video. I reached the point where he said:
such tricky puzzles involve castling or… I paused the video here and thought about it and it was obvious
The layout is impossible due to there being all the pieces on the board but pawns that need to have captured to get where they are. Also even if the position was legal the convention in chess puzzles is that En passant is only used if you can prove by deduction that the last move was a pawn jump All in all a badly presented puzzle, although I spotted the “answer” straight away.
Yeah I didn’t notice the pawns though I don’t think it’s crucial to the solution. I didn’t know about the convention. I would imagine the puzzle is obvious if you have seen the basic idea before but I haven’t so I enjoyed it.
You need special knowledge to allow for an en passant capture in this case and a solution to the puzzle. Without the prior pawn move, the solution presented is not a legal move and the one-move mate cannot happen. However, it is clever.
Yeah, I’m going to chime in on the “no” side, too. It’s always a rule in chess puzzles that it must be possible to reach the given position, and that’s especially true for a puzzle that depends on knowing how we got to that position. You’re more justified to say “there was no previous move” than you are to say “the pawn move was the previous move”. Or you can say that the winning move must be pawn to G8, because obviously these are magic pawns who can move to wherever they want.
Mr. Shine and Chronos are quite correct.
Chess problems have to be a legal position and you can only capture en passant if you can prove the last move by the opponent allowed it.
My cite is the World Chess Solving Championships (which I’ve taken part in. 
)
Here’s a problem I composed:
White: King h5, Rook f8, Bishop h8, pawns h6, f7, f6, f5
Black: King h7, pawn g5
White to play and mate in one.
Black’s last move must have been pawn g7-g5, so White mates by pawn f5xg6 en passant.
(For fun, how did the bishop on h8 get there?)
Since Black had a pawn on g7 last move, the bishop must be a promoted pawn.
Woot…solved it in my head, though it took a little while to ‘set the board’ in my mind.
As for the second part, I don’t see why, other than that it may not have been White’s last previous move.
Very clever. Thank you.
Meh. I’ve never heard of this convention, but I solved it in 31 seconds, according to the Youtube time bar. I don’t understand the objections…it is proven what the last move was because the puzzle says “Mate in 1” and there isn’t any other solution. That’s all the proof you need.
I solved it, though it took me more like two minutes, but I treated the question as a trick question of some sort as “There is a checkmate in 1. In what case is that possible?” And, in that case, there is only one answer. I first started on some ridiculous train of thought that the “up” side of the board was actually white and the “down” side of the board was actually black as the “trick,” as ridiculous as that seemed, and it did prove to be a stupid train of thought, but the next one was to look for unusual moves like en passants, and that solved it rather quickly.
And, Christ, could they not use more distinguishable colors for the chess pieces? I could barely tell black from white apart and had to google “most difficult checkmate in 1” to get an image that didn’t make my eyes hurt.
My father (who was a good chess player) and I (who was not) tried to figure out the shortest game possible. We got down to three moves.
White’s queen knight moves three times, ending on F6. Black has used those three moves to move the king and king knight pawns, and the king knight to H6.
Purely a theoretical exercise, of course. In real games, my father needed at least five moves to beat me.
What about the two-move Fool’s Mate? I mean, you have to play idiotically to fall into it, but that’s the classic short mate. A more plausible one is the Scholar’s mate. I actually did fool my friend into it when I was in seventh grade. He was not happy and proceeded to kick me in the shins.
Is there an online site where I can see that set up? I don’t have a board, and I can’t really picture it in my head.
My brother was a stronger player than I was as a kid, but I did get him with a Scholar’s Mate once. And that was before we encountered it in a book or knew that it had a name, so I can legitimately claim to have discovered it independently.
As they used to say on Perry Mason, the puzzle “assumes things not in evidence.”
I found one, actually. Let’s see if a link works. Link.
Very clever what you did there. It’s more subtle than I thought at first.[spoiler]Black has only the king and a pawn. Every square the king could have moved from is under attack from a white piece. It’s possible that the black king was moving out of check on it’s last move, but every square it could have moved from is under attack from two white pieces. There’s no scenario by which white could have put the black king in check, leading it to move to its current position. So the black king could not have made the most recent move.
If it wasn’t the black king that moved last, it must have been the black pawn. And the black pawn could not have been on g6 before moving because that would have put the white king in check. The black pawn must have been on g7, and moved two spaces.[/spoiler]How long did it take you to come up with this?
never mind, ninjad by about 14 minutes. Must have had the screen on for a while and come back to it without refreshing 
Thank you for posting the position (please feel free to post the two positions below!)
Well I have a long-standing interest in chess problems and retro-analysis of chess positions.
So maybe 5 minutes. 
I use that position to help beginners understand en passant.
If you like that position, here are two others I made up to explain ‘special’ moves in chess:
White: King e1, Rook h1, Bishops f4, c8, Knight c3
Black: King f3
White to play and mate in one.
Castles King-side (in chess problems you are allowed to assume Castling is permitted unless it can be proven it was impossible)
White: King e5, Rook a8, Bishop f6 pawn h7
Black: King f7
White to play and mate in one.
pawn h7-h8 = Knight
Bonus question: What happens after 1. Ke5-f5?
It’s Stalemate (automatic draw)
Minor correction to your spoiler:
White’s queen knight moves three times, ending on F6. Black has used those three moves to move the king and king knight pawns, and the king knight to e7.
Another 3 move mate:
The Scholar’s Mate is the trick my father pulled on me whenever he decided I had been playing too much by my plan and not enough anticipating my opponent’s moves. I won’t tell you how many times I fell for that over the years, except to remind you that I wasn’t a particularly good player.
Assumes facts not in evidence. How do you know that this board position can be arrived at through conventional play? It might not be, as some puzzles are strictly setups. If so, you need to specify the previous pawn move or invent one.