The phrase "h.t.d.," seemingly a code for sex, appears frequently in A Celtic Temperament, a recently published collection of Robertson Davies' diaries. E.g.:

"H.t.d. in sunroom, best in many months."

"Chat with Brenda in the evening and unusually fine h.t.d. and early to sleep."

Quill and Quire speculates that h.t.d. may stand for "high tempo debauchery."

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