Discretion

Melanie Bush claimed that discretion was her middle name. (TV: Delta and the Bannermen)

It was often said that discretion was the better part of valour. This phrase was used by the First, (TV: The Chase) Second, (TV: The Abominable Snowmen) Fourth, (TV: The Ark in Space) and Sixth Doctors. (TV: The Twin Dilemma, The Mark of the Rani)

John, the landlord of 11 Cardinal Road, claimed that discretion was second nature to a man such as himself. (TV: Knock Knock)

Dorium Maldovar once described the The Silence as "a religious order of great power and discretion." (TV: The Wedding of River Song)