Leslie Stephen,
Dictionary of National Biography…
(1893)
“ Mary's devotion to the catholic religion—the religion of her mother—was the central feature of her life and character. Filial piety forbade, in her view, any wavering in her adherence to the pope, who had identified himself with her mother's cause. Similar sentiments underlay her regard for her cousin Charles V, on whose advice she relied in the chief crises of her life. Only half an Englishwoman, she did not recognise the imprudence of identifying herself with her Spanish kinsmen, and to her blindness in that regard must be attributed her marriage—the great error of her life. ”
