Ya tafi Ingila a watan Yunin 1941, inda aka haɗa shi da Ofishin Jakadancin Amurka a London a matsayin Mataimakin Naval Attaché. A watan Satumba na wannan shekarar, ya dauki nauyin aiki a matsayin Mai Kula da Sojojin Ruwa na Musamman da kuma ƙarin aiki a kan ma'aikatan Babban, Ayyukan Hadawa (Birtaniya) a matsayin mai koyarwa a yakin amphibious, kuma an nada shi zuwa mukamin colonel a watan Disamba na 1941. A watan Yulin 1942, Hart ya shiga cikin
Dieppe Operation, wanda aka yaba masa musamman don kyakkyawan hali daga Lord Louis Mountbatten, Shugaban Ayyukan Hadawa. Ya kasance a Ingila har zuwa Oktoba 1942, lokacin da ya koma Amurka don zama memba na Ma'aikatan Kwamandan Kwamandan, Amurka, Navy Department, Washington, D.C., a matsayin Shugaba, Tsarin Tsarin Gaba.