▁its ▁way ▁to ▁becoming ▁oper ational , ▁and ▁the ▁Br istol ▁B len heim ▁was ▁increasing ly ▁available ▁for ▁fitting . ▁The ▁first ▁prototype ▁system ▁went ▁into ▁service ▁in ▁November ▁ 1 9 3 9 , ▁long ▁before ▁the ▁opening ▁of ▁major ▁British ▁operations . ▁Several ▁improved ▁versions ▁followed , ▁and ▁by ▁the ▁time ▁the ▁Bl itz ▁opened ▁in ▁August ▁ 1 9 4 0 , ▁the ▁A I ▁M k . IV ▁was ▁available , ▁offering ▁greatly ▁improved ▁performance ▁with ▁a ▁range ▁between ▁ 2 0 , 0 0 0 ▁and ▁ 4 0 0 ▁feet , ▁and ▁installation ▁had ▁begun ▁in ▁July ▁ 1 9 4 0 . ▁This ▁greatly ▁reduced ▁the ▁load ▁on ▁the ▁Ch ain ▁Home ▁ground - control led ▁inter ception ▁component ▁of ▁the ▁night - fig h ter ▁system , ▁who ▁only ▁had ▁to ▁get ▁the ▁f ighter ▁within ▁four ▁miles ▁before ▁the ▁f ighter ' s ▁rad ar ▁would ▁be ▁able ▁to ▁let ▁them ▁take ▁over ▁during ▁the ▁attack . ▁Due ▁to ▁the ▁relatively ▁low ▁performance ▁of ▁the ▁B len heim ▁( a ▁converted ▁bom ber ) ▁the ▁British ▁experiment ed ▁with ▁using ▁R DF - equ ipped ▁Douglas ▁Hav oc ▁bom bers ▁converted ▁to ▁carry ▁a ▁search light , ▁ill umin ating ▁the ▁enemy ▁aircraft ▁for ▁accomp any ing ▁H urr icane ▁single - engine ▁f igh ters ▁to ▁shoot ▁down . ▁Kn own ▁as ▁the ▁Tur bin l ite , ▁the ▁idea ▁was ▁not ▁a ▁success , ▁and ▁in ▁time , ▁both ▁the ▁B