At the beginning of the episode, the lawn is seen uncovered by chessboard squares; a few moments later, it is shown as the chessboard. The chessboard remained in place for a week during September 1966 during filming of this episode; when it was removed, the grass had been lightened and the pattern is clearly visible in prior episodes.
The boat used to film the "SS Polotska" sequences also features in "Many Happy Returns" as the gun runners' boat.
The chess game is recreated annually by Prisoner fans at their annual convention, held at Portmeirion.
Checkmate received the highest viewing figures of any of the series' episodes on its UK premiere.
The human chess game proved very complex to film, and to plan out, and commenced shooting two days late.