Whakaotihia te rerenga e whai ake nei: I te marama o Hepetema 1796, i tohua a Johnston hei kaitiaki o te puni ki te Kawana a John Hunter, a i te tau 1800 i whakawhiwhia ki a ia tana tohu tohu hei rangatira nui. I taua tau ano i mauheretia a Johnston e te Kawana Lieutenant William Paterson mo nga whakapae mo te "utu i nga wairua ki tetahi kaitiaki hei waahanga o tana utu" me te tutu ki nga whakahau. I whakahe a Johnston ki te whakawakanga a te kooti hoia i te koroni, a ka tukuna ia e Hunter ki Ingarangi. I reira ko nga uaua o te whakahaere i te whakawakanga me nga kaiwhakaatu i Ahitereiria i arahi ki te whakakore i nga mahi, a ka hoki a Johnston ki New South Wales i te tau 1802. I te tau 1803 ka riro a Johnston hei rangatira mo te wa poto mo te New South Wales Corps i te wa e mate ana a Paterson, a ka uru ki te pakanga i waenga i a King me te ope taua. I te Poutu-te-rangi 1804 i mahi ia ki te whakatau ina i roto i te whakahau o te hōia tonoa ki etahi
he herehere i whakakeke i Castle Hill. I te wa i tukuna ai a Paterson ki Port Dalrymple, ko Johnston te rangatira o te New South Wales Corps.