‘HAVE’ to have + PAST PARTICIPLE
Here’s an example of past modality:
You HAD TO HAVE KNOWN about the problem before you started driving.
Before the car broke down on the highway, I am sure you noticed something was wrong with the car.
conclusion
You must be | It must be
In the English Grammar Profile, B1 point 69 in the category of MODALITY is defined: DEDUCTIONS AND CONCLUSIONS: ‘must’ to guess and deduce, most commonly with ‘it must be’, or ‘you must be’. *We cannot ensure automatically that this form will point to the usage. We have deleted some ngrams that are obviously not the …
MUST HAVE + past participle
In the English Grammar Profile, there are essentially the same two points in the category of Modality at B2 for the same form. Point 144 is defined as: DEDUCTIONS AND CONCLUSIONS: perfect form of ‘must’ to make deductions about the past. and point 166: PAST AFFIRMATIVE must have’ + ‘-ed’. For example: He had come such a long way, and his dream must have seemed so close that he could …