On top of:
I found one occurrence of "on the top of" in the Corpus Concordancer. I searched the BNC Written (1,007,000 words) and it produced this:
"The night-light glowed softly ON THE TOP OF the chest of drawers."
This refers to a very specific place: a particular location on the top of a piece of furniture. Much more often, we have "on top of" as an adverbial or prepositional phrase. See these examples:
"This at a time when our much valued and valuable oil revenues are at their height and on top of this our currency continually drops in value abroad."
"The VAT on fuel (...) came on top of the expected rise in road tax duty, tobacco and alcohol duty (...)"
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