reported speech

"You must be seated in the restaurant by half past six tonight," Miss Goh reminded her guests.

In reported speech, should I use 'must' or 'had to be' or is either fine?

Mrs Goh reminded her guests that they must / had to be in the restaurant by half past six that night.

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You could use either, T but 'had to' would be the normal neutral, and especially this case where it seems somwhat distant in time, by using "that night".

If it was being reported soon after 'must' or 'have to' would probably be used.

Ms Goh says/said that you have to/must be in the ...

Do you know a Ms Goh?

Is she a "Goh-er"? (I'll get my coat)

Miss Goh reminded her guests that they were required to be seated in the restaurant by half past six that evening.

Half past six is hardly "night".

"Half past six is hardly "night"."

That depends on the latitude and the season, Contrex.