mustn´t in the past tense


What is the most precise or correct expression of mustn´t in the past tense?

I mustn´t go to work, the doctor said.

I mean from the semantic point of view, because there are several possibilities as wasn´t allowed to, couldn´t, etc. but which one is the most exact?


“I wasn’t allowed to” (or similar) works if “I mustn’t” means “I’m not allowed to” (i.e. someone is forbidding it). However, “I mustn’t” more often suggests a self-imposed restriction (“I mustn’t eat any more of those chocolates!”), in which case I can think of no past tense form without becoming very verbose. Although “I shouldn’t…” is close in the present tense, “I shouldn’t have…” has a different nuance, suggesting that actually you did. I can’t think of any sense of “I mustn’t” for which “I couldn’t” is a reasonable past tense. Sorry, you might be able to use “couldn’t” in the sense of “wasn’t allowed to”; I was thinking of the sense “wasn’t able to”. (I knew I shouldn’t have embarked on this question!)

By the way, you are using the wrong character for the apostrophe. You seem to be using an acute accent (´). See if you can find on your keyboard the character ’ or ’.