This is a follow-up question to this earlier question on instances where the fielding team did not appeal for a wicket.
Are there any recorded instances where the batsman chose to walk, after realising that they have nicked the ball, without any appeal from the fielding side?
This would of course constitute exemplary sportsmanship, and the chances of such an instance would be extremely low in the modern era where the game has become increasingly competitive.
For the sake of this question, all international formats of the game, first class and upper levels of domestic cricket can be considered.