During their original run of The Original Series, the BBC had chosen not to show the episodes "The Empath", "Whom Gods Destroy", and "Plato's Stepchildren", deeming them unsuitable for the series time slot, due to their assessment that "(...) they all dealt most unpleasantly with the already unpleasant subjects of madness, torture, sadism and disease", as stated in a letter sent to the UK-based Star Trek Action Group in 1976. These episodes were eventually shown during the 1992 repeat run. "Miri" was not repeated by the BBC until 1993 for similar reasons, following audience complaints after its original transmission. (Star Trek Magazine issue 177, p. 33)
That lines up with what other other sites say, that it is four: