Looks familiar but New!

• One might think ... obviously the Black Rook can take White Rook (E8 to G8), but ...
• The White Rook at F7 is the piece that checkmates the Black King. 
• He's protected by the White Knight at F5! 
• And the White Knight is protected by the White Pawn at G4!
• Black King trapped! And mated!
• My initial strategy was to pick off the Black Pawn at C7 ... but this developed somewhat unexpectedly