 In May 1996 , the National Gallery took on loan <unk> 's Innocent X portrait and hung it alongside four <unk> paintings ; Head VI , Pope I ( 1951 ) , Pope 1961 and Pope 1965 . <unk> believes that <unk> would have disapproved of such a showing with a work he considered one of the finest ever painted , but writes that two , including Head VI , " stood up to it , and even enhanced its authority as one of the most penetrating studies of human nature and human power " . 
