David2009: The position at the start of the NN vs P ending (White to play): 
click for larger view White started well with 68 Ne4 and Black played the cunning move 68 Kg7!?. In theory this should have lost more quickly than 68 Kh5, in practice it gave White the chance to make a mistake. White should have played 69. Nd6, e.g. 69... Kg6 70 Nf7 which drives Black first to the h file and then towards either the h1 or h8 corners. There is a mate if Black can be confined anywhere near these corners since White has 5 spare moves up to and including Black's queening move to manouevre a checkmate. Instead White made an instructive mistake: 69 Kf5? This allowed Black to move towards the blockading N, and then to shelter near it. The win is then very difficult (Black cannot readily be forced away from it, see game) and indeed the shortest winning method is to release the Pawn. One ends up allowing:
click for larger viewThis is won for White only if it is Black's move: with White to move it is drawn. Moral- these endings are harder than they look! | 
