I had High Tea with 1pm reservation weekday. Based on what was served to us, lunchtime should be no problem for them. Wasn't busy, I think reservations are for the meal prep rather than not having a long wait.
It should be able to. I went at 2pm when I visited, a traditional time for tea, but you should be able to order High Tea during any of their business hours. Just call ahead to make a reservation and you're all set.
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