▁test ▁programme . ▁ ▁Can cellation ▁It ▁was ▁ 1 9 5 7 ▁before ▁the ▁first ▁SR . 5 3 ▁took ▁to ▁the ▁air , ▁just ▁over ▁a ▁month ▁after ▁the ▁inf am ous ▁ 1 9 5 7 ▁Def ence ▁White ▁P aper ▁had ▁been ▁published ▁out lin ing ▁the ▁British ▁government ' s ▁policy ▁to ▁largely ▁abandon ▁pil oted ▁aircraft ▁in ▁favour ▁of ▁concentr ating ▁on ▁miss ile ▁development . ▁At ▁the ▁same ▁time , ▁jet ▁engine ▁development ▁had ▁progress ed ▁a ▁long ▁way ▁in ▁the ▁six ▁years ▁since ▁the ▁SR . 5 3 ' s ▁initial ▁design . ▁Com b ined ▁with ▁the ▁fact ▁that ▁improvements ▁in ▁rad ar ▁had ▁meant ▁that ▁any ▁incoming ▁bom ber ▁threat ▁could ▁be ▁detected ▁much ▁earlier , ▁the ▁need ▁for ▁an ▁aircraft ▁like ▁the ▁SR . 5 3 ▁had ▁disappeared , ▁and ▁the ▁project ▁was ▁cancel led ▁on ▁ 2 9 ▁July ▁ 1 9 6 0 , ▁with ▁the ▁third ▁prototype ▁( X D 1 5 3 ) ▁never ▁built . ▁ ▁A ircraft ▁on ▁display ▁The ▁first ▁SR . 5 3 ▁prototype , ▁X D 1 4 5 , ▁is ▁preserved ▁at ▁the ▁Royal ▁Air ▁Force ▁Museum ▁Cos ford ▁near ▁Wol ver ham pton . ▁ ▁Oper ators ▁ ▁Ministry ▁of ▁Supp ly ▁ ▁Spec ifications ▁ ▁See ▁also ▁ ▁References ▁ ▁Notes ▁ ▁Bibli ography ▁▁ ▁Jones , ▁Barry . ▁" S aro ' s ▁M ixed ▁Power ▁S aga ". ▁Aer op lane ▁Month ly , ▁November ▁ 1 9