King only

Originally posted by davidtravelling
I am currently in a game with an opponent who i have whittled down to a king, it is taking me ages to get him into a mate position. My friend told me that in chess once one side is down to king you only have 20 moves to mate him, is this true?

Here are the FIDE (the official world chess organization) on how a game can end. Probably the last paragraph of 5.2 is the relevant one to your situation (I didn't check the game). There are no other rules.

"Article 5: The completion of the game

5.1 The game is won by the player who has checkmated his opponent's king. This immediately ends the game, provided that the move producing the checkmate position was a legal move.

The game is won by the player whose opponent declares he resigns. This immediately ends the game.

5.2 The game is drawn when the player to move has no legal move and his king is not in check. The game is said to end in 'stalemate'. This immediately ends the game, provided that the move producing the stalemate position was legal.

The game is drawn when a position has arisen in which neither player can checkmate the opponent's king with any series of legal moves. The game is said to end in a 'dead position'. This immediately ends the game, provided that the move producing the position was legal.

The game is drawn upon agreement between the two players during the game. This immediately ends the game. (See Article 9.1)

The game may be drawn if any identical position is about to appear or has appeared on the chessboard at least three times. (See Article 9.2)

The game may be drawn if each player has made the last 50 consecutive moves without the movement of any pawn and without the capture of any piece. (See Article 9.3)