▁oppos ing ▁Soviet ▁aircraft ; ▁by ▁the ▁early ▁ 1 9 6 0 s , ▁it ▁was ▁sus pected ▁that ▁these ▁bom bers ▁might ▁well ▁be ▁capable ▁of ▁su person ic ▁spe eds ▁of ▁up ▁to ▁Mach ▁ 2 ▁with ▁a ▁potential ▁oper ational ▁alt itude ▁as ▁high ▁as ▁. ▁According ly , ▁a ▁capable ▁defence ▁inter ceptor ▁that ▁could ▁form ▁part ▁of ▁the ▁nation ' s ▁measures ▁to ▁counter ▁this ▁threat ▁would ▁need ▁to ▁be ▁capable ▁of ▁similar ▁spe eds ▁and ▁an ▁exception ally ▁high ▁rate ▁of ▁clim b ▁in ▁order ▁to ▁reach ▁high ▁alt itude ▁bom bers ▁in ▁time . ▁ ▁The ▁development ▁of ▁the ▁Spr ite ▁and ▁the ▁Sn ar ler ▁had ▁led ▁to ▁the ▁possibility ▁of ▁a ▁more ▁powerful ▁ro cket ▁engine ▁being ▁developed ▁as ▁the ▁planned ▁power plant ▁for ▁a ▁vi able ▁" point ▁defence " ▁inter ceptor . ▁The ▁requirements ▁of ▁O . R . ▁ 3 0 1 ▁were ▁considered ▁on er ous , ▁including ▁a ▁r amp ▁launch ▁and ▁landing ▁on ▁a ▁sk id , ▁and ▁with ▁the ▁comp liance ▁of ▁the ▁companies ▁which ▁had ▁approached ▁to ▁tender , ▁the ▁am ended ▁Spec ification ▁F 1 2 4 T ▁allowed ▁for ▁a ▁mixed ▁power plant ▁configuration ▁along ▁with ▁the ▁ad option ▁of ▁a ▁conventional ▁under car riage . ▁On ▁ 2 1 ▁February ▁ 1 9 5 1 , ▁the ▁re vised ▁Spec ification ▁F 1 2 4 T ▁was ▁circul ated ▁to ▁half ▁a ▁dozen ▁of ▁Britain ' s ▁various ▁aircraft ▁manufact ur ers