▁Part ▁I ▁in ▁ 1 9 3 0 ▁and ▁Part ▁II ▁in ▁ 1 9 3 1 , ▁gradu ating ▁with ▁a ▁Bach elor ▁of ▁Arts ▁( BA ) ▁degree . ▁Having ▁special ised ▁in ▁physics ▁in ▁Part ▁II , ▁he ▁was ▁ad vised ▁by ▁Lord ▁R uther ford ▁to ▁return ▁to ▁B irmingham ▁to ▁undert ake ▁his ▁clin ical ▁training . ▁He ▁did ▁so ▁and ▁graduated ▁Bach elor ▁of ▁Medicine , ▁Bach elor ▁of ▁S urg ery ▁( MB ▁B Ch ir ) ▁from ▁the ▁University ▁of ▁Cambridge ▁in ▁ 1 9 3 4 . ▁ ▁Career ▁Mitchell ▁began ▁his ▁medical ▁career ▁as ▁a ▁house ▁officer ▁at ▁B irmingham ▁General ▁Hospital . ▁He ▁returned ▁to ▁the ▁University ▁of ▁Cambridge ▁as ▁a ▁post grad uate ▁studying ▁under ▁Sir ▁Eric ▁R ide al . ▁During ▁this ▁time , ▁he ▁held ▁the ▁El more ▁research ▁student ship ▁and ▁then ▁the ▁Beit ▁Memorial ▁Fellow ship ▁for ▁Medical ▁Research . ▁He ▁was ▁elected ▁a ▁fellow ▁of ▁St ▁John ' s ▁College , ▁Cambridge ▁in ▁ 1 9 3 6 . ▁In ▁ 1 9 3 7 , ▁he ▁completed ▁his ▁Doctor ▁of ▁Philosoph y ▁( Ph D ) ▁degree ▁on ▁' the ▁ir rad iation ▁of ▁thin ▁protein ▁films '. ▁ ▁From ▁ 1 9 3 7 ▁to ▁ 1 9 3 8 , ▁he ▁worked ▁as ▁a ▁radi ological ▁officer ▁at ▁the ▁Christ ie ▁Hospital , ▁a ▁centre ▁that ▁special ised ▁in ▁the ▁treatment ▁of ▁cancer , ▁based ▁in ▁Manchester . ▁In ▁ 1 9 3