If we celebrated the US Bicentennial on July 4, 1979 and will be celebrating, just for example, the California Sesquicentennial on September 9, 2000, what will we be celebrating on July 4, 2029? The Sesquibicentennial? None of my dictionaries are looking that far ahead. I note that "sesquicentennial" is considered an Americanism. Have our British cousins never celebrated the 150th anniversary of anything? I also note that AWAD does not have the word in its database.

Excellency will do.
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Excellency will do.