Restrictions on the religious cult did not prevent the continuation of a secular cult of Ferdinand, connected to the narrative that Ferdinand was a voluntary martyr for Portugal's imperial mission. The Portuguese poet Luís de Camões made a brief mention of Ferdinand in his epic 1572 poem "Os Lusíadas" (Canto IV, stanzas 52–53), asserting Ferdinand had given himself to martyrdom voluntarily for patriotic reasons, "a sacrifice to love of country made, that not for him strong Ceuta be o'erthrown, the public weal preferring to his own." Perhaps surprisingly, the Fernandine legend got another gust of wind after the 1580 Iberian Union with Spain. The Spanish playwright composed a drama "La Fortuna Adversa del Infante D. Fernando de Portugal" in 1595–98 (sometimes attributed to Lope de Vega), which was probably the basis for the more famous 1629 Baroque play "El príncipe constante" by Calderón.