ˌɔn pɐtɹˈoʊl ˌɔn twˈɛnti wˈʌn mˈeɪ, ɐwˈeɪɾɪŋ ðə dᵻpˈɑːɹtʃɚɹ ʌvðə kˈɑːnvɔɪ ˌɔn ɪts ɹᵻtˈɜːn vˈɔɪɪdʒ, nˈiːldz ɹᵻsˈiːvd ɐ sˈʌbmɚɹˌiːn kˈɑːntækt ɹᵻpˈoːɹt fɹʌm ɐ bɹˈɪɾɪʃ ɑːbzɚvˈeɪʃən plˈeɪn ænd ɪmˈiːdɪətli hˈɛdᵻd fɚðɪ ˈɛɹiə.
On patrol on 21 May, awaiting the departure of the convoy on its return voyage, Nields received a submarine contact report from a British observation plane and immediately headed for the area.