Had Troilus lived to adulthood, the First Vatican Mythographer claimed, Troy would have been invincible; however, the motif is older and found already in Plautus' Bacchides.
hæd tɹˈɔɪləs lˈɪvd tʊ ɐdˈʌlthʊd, ðə fˈɜːst vˈæɾɪkən mɪθˈɑːɡɹəfɚ klˈeɪmd, tɹˈɔɪ wʊdhɐv bˌɪn ɪnvˈɪnsᵻbəl; haʊˈɛvɚ, ðə moʊtˈiːf ɪz ˈoʊldɚ ænd fˈaʊnd ɔːlɹˌɛdi ɪn plˈɔːɾəs bˈækaɪdz.