The past simple and past perfect tenses (BBC Learners' Questions)

source: BBC Learning English          2017年8月18日
This week's learner question comes from Niki from Hungary, who writes: The following sentence has been giving me a headache for weeks now. Could you please give me the correct answer and justify it? When was the last time you had eaten / ate in this restaurant? Two weeks ago.
Dan has the answer.
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