Best of three
Best of three was, according to the Fourteenth Doctor "an inviolable rule" that two players who were one-all were compelled to follow. The rule stated that the two players must have a third and final game to determine to true winner between them. Then, and only then, could the winner claim their prize for victory.
The Doctor enacted this rule shortly in shortly after he lost a game of Cut in Soho, 1925, against the Toymaker, given the Toymaker had now won one game (TV: The Giggle [+]Loading...["The Giggle (TV story)"]) and the Doctor's first incarnation had won their last game "many years ago". (TV: The Celestial Toymaker [+]Loading...["The Celestial Toymaker (TV story)"]) Even though the Toymaker initially fled to 2023 and tormented members of UNIT, the Doctor insisted he had grant him one more game, because the rule meant that he "owed" it to him. (TV: The Giggle [+]Loading...["The Giggle (TV story)"])