‘A shudder in the loins engenders there/ The broken wall, the burning roof and tower/ And Agamemnon dead’ intoned W.B. Yeats in his sonnet ‘Leda and the Swan’, seeing in this avian rape the germ of the Trojan war. Leda gave birth to Helen of Troy and her sister Clytemnestra, the one renowned as the casus belli, the other the most infamous agent of the aftermath.