Sheikha Al Mayassa, sister of the emir of Qatar, is by more than one account the most powerful person in the art world due to her position as head of the free-spending and ridiculously well-funded Qatar Museums Authority. Whenever the sheikha is in town, ”everyone from government ministers to mayors queue up to pay their respects,” said ArtReview, which ranked her at the top of its Power 100 list of the art world’s most influential people.