...No surprises there, though Black's oversight that allowed this was an easy one to make. The (half) pin on the f-file forces Black to retake with the d-pawn, and that frees up White's d-pawn.

Not a fatal mistake yet, but it will be interesting to see Black disrupt the play a bit to keep the pawn advances to a minimum.

Actually I think I have made a fatal mistake, and there is no way back for black now.

I was expecting 22.d6, here, though, with the idea 22...Ne6 23.Bxb5. Black would have had to try 22...Rad8 or 22...Qd7 and try to hang on after, say 23.a4 bxa4 24.c4! with a sudden onslaught of pawns.

But d6 now has the reply Qd7! No need to rush it.

I imagine 23...Ne6 24.c4 Nd4 25.c5 ... didn't fill Black with confidence... But indications are that it might have been the preferable option.

Would 23...Rd7 here been a possibility?

Agreed with Ion's line. It looks to me like the best continuation. @5imon if 23.Rd7? then 24.Qe3! heading to c5 threatening the b5 pawn and potentially the knight again if it moves to d5.

It makes sense: if dxN, RxQ, RxR, Qxc7 and black seems ok... so black can leave the N whre it is, isn't it?

I was expecting 24.Bxb4 Nxd6 25.Bc6 here, or 24.Bxb4 Rxd6?? 25.Bxf8. Seems White had more than one good move available!

Bxb4 is good, but seems slower to me.

Why not to take the pawn? After 24. Bxb5, it seems black has a good answer by taking the pawn, but if ...Rxd6, 25. BxNe8! and white wins material. So black plays ...Nxd6. White plays 26. Bc6, threatening Ra8, but mostly Bd5, and "seemingly" allowing ideas like ...Nc4? This leads to this spectacular mate: 27. Qxd8+, RxQ, 28. RxR+, Qf8 (black square, it seems white will exchange, but... 29. Bd5+! and mate.

Well found! Actually black can avoid mate with 28....Qe8 but I lose the queen and end up two rooks down.

I'm guessng a 'removing the guard' temporary sacrifice to win material - at least a minor piece.

You betcha I would have played it. Had you been playing White, Charles, you would have seen it in a twinkling, and played it yourself. The problem is that with the Black pieces, Black's position was already seriously compromised.

Exactly what I had in mind.

You raise an interesting point, Joe, in respect of thought processes. White would like to pin the Black Queen, but that, as you see, is not possible right off. But the canny player thinks to himself, 'Bc4 won't do, but can I arrange - or threaten to arrange - the bishop's appearance on the crucial diagonal so that I CAN pin the queen? Alternatively, can I use that idea as a threat in order to make some other gain?' By threatening to take the rook and follow up with the d-pawn's promotion, white also threatens the pin. Note the 'fork', here. Just as the a8-rook is being attacked, so is the d5-square - a key point. Black is now in very serious trouble, and has a losing game.

Wonderfully explained, archduke!

Probably 28...Rxd7 was the best Black could hope for. Now White has a brief combination to exchange down to an easy win. Clue: Black's back rank!

! Best, I reckon.

Black's quietus will come quickly now.

The key being the very last move - and no one else. Otherwise, the exchanges would be even and harmless! Wonderful sight, wonderful move.