6 8 ) ▁were ▁released ▁for ▁direct ▁purchase ▁by ▁the ▁R AF ▁where ▁it ▁was ▁given ▁the ▁service ▁name ▁Liber ator ▁B . M k . I ▁( from ▁" B om ber ▁Mark ▁ 1 "). ▁ ▁The ▁twenty ▁Liber ator ▁B . M k . I ▁were ▁delivered ▁to ▁the ▁R AF ▁starting ▁in ▁mid ▁ 1 9 4 1 ▁and ▁were ▁given ▁serial ▁numbers ▁AM 9 1 0 ▁to ▁AM 9 2 9 . ▁ ▁After ▁a ▁period ▁of ▁testing ▁at ▁the ▁Aer op lane ▁and ▁Arm ament ▁Ex perimental ▁Est ab lish ment ▁( A & AE E ) ▁at ▁R AF ▁Bos com be ▁Down , ▁England , ▁it ▁was ▁found ▁to ▁be ▁un su itable ▁for ▁combat ▁over ▁Europe . ▁Among ▁the ▁def ic ien cies ▁c ited ▁were ▁the ▁lack ▁of ▁self - se aling ▁fuel ▁t anks , ▁poor ▁def ensive ▁arm ament ▁and ▁general ▁lack ▁of ▁combat ▁read iness . ▁ ▁The ▁long ▁range ▁and ▁heavy ▁bomb ▁load ▁however , ▁made ▁the ▁Liber ator ▁a ▁natural ▁choice ▁for ▁R AF ▁Coast al ▁Command ▁( CC ) ▁for ▁use ▁in ▁long - range ▁mar itime ▁pat rol s ▁against ▁the ▁U - bo at ▁men ace . ▁Tw elve ▁aircraft ▁were ▁sent ▁to ▁Scottish ▁A viation ▁in ▁Pr est wick , ▁Scotland ▁for ▁extensive ▁conversion ▁to ▁meet ▁the ▁anti - sub marine ▁war fare ▁role ▁and ▁they ▁were ▁red es ign ated ▁Liber ator ▁GR . M k . I ▁– ▁the ▁' GR '