▁powerful ▁flu ores cent ▁d ye ▁for ▁spot ting ▁of ▁a ▁down ed ▁air man ▁at ▁sea . ▁ ▁In ▁an ▁example ▁of ▁later al ▁thinking , ▁F ras er - Smith ▁used ▁a ▁special ▁left - hand ▁thread ▁for ▁the ▁dis gu ised ▁sc rew - off ▁top ▁of ▁a ▁hidden - document ▁container ; ▁he ▁suggested ▁this ▁would ▁prevent ▁discovery ▁by ▁the ▁" un swer ving ▁logic ▁of ▁the ▁German ▁mind ", ▁as ▁no ▁German ▁would ▁ever ▁think ▁of ▁trying ▁to ▁uns cre w ▁something ▁the ▁wrong ▁way . ▁ ▁At ▁one ▁point ▁his ▁exp enses ▁were ▁challeng ed ▁by ▁a ▁senior ▁Tre as ury ▁official ▁over ▁the ▁extra v ag ant ▁costs ▁of ▁an ▁order ▁for ▁packets ▁of ▁ 1 2 ▁raz or ▁bl ades . ▁ ▁F ras er - Smith ▁asked ▁for ▁a ▁tre as ury ▁cost ing ▁cl erk ▁to ▁accomp any ▁him ▁on ▁a ▁visit ▁to ▁the ▁company ▁to ▁determine ▁whether ▁or ▁not ▁they ▁were ▁prof ite ering . ▁ ▁After ▁checking ▁that ▁the ▁cl erk ▁had ▁signed ▁the ▁Official ▁Sec rets ▁Act , ▁the ▁cl erk ▁review ed ▁the ▁costs , ▁which ▁were ▁in ▁fact ▁for ▁a ▁top - secret ▁k it ▁designed ▁to ▁aid ▁SO E ▁agents ▁with ▁escape ▁and ▁ev asion . ▁The ▁cl erk ▁discovered ▁that ▁the ▁company ▁was ▁in ▁fact ▁under charg ing ▁as ▁they ▁had ▁not ▁claimed ▁the ▁reg ulation ▁profit . ▁As ▁a ▁result , ▁the ▁supp lier ▁was ▁directed ▁to ▁submit ▁a ▁new ▁in voice ▁with ▁every ▁item