▁ca es ium ▁standard ▁atomic ▁clock ▁was ▁carried ▁out ▁by ▁the ▁use ▁of ▁the ▁astronom ical ▁time ▁scale ▁e ph emer is ▁time ▁( ET ). ▁This ▁led ▁to ▁the ▁intern ation ally ▁agreed ▁definition ▁of ▁the ▁latest ▁SI ▁second ▁being ▁based ▁on ▁atomic ▁time . ▁ ▁Comput ing ▁N PL ▁has ▁undert aken ▁computer ▁research ▁since ▁the ▁mid - 1 9 4 0 s . ▁From ▁ 1 9 4 5 , ▁Alan ▁T uring ▁led ▁the ▁design ▁of ▁the ▁Autom atic ▁Comput ing ▁Engine ▁( ACE ) ▁computer . ▁The ▁A CE ▁project ▁was ▁over amb it ious ▁and ▁fl ound ered , ▁leading ▁to ▁T uring ' s ▁departure . ▁Donald ▁Dav ies ▁took ▁the ▁project ▁over ▁and ▁concentr ated ▁on ▁deliver ing ▁the ▁less ▁am bit ious ▁Pil ot ▁A CE ▁computer , ▁which ▁first ▁worked ▁in ▁May ▁ 1 9 5 0 . ▁Among ▁those ▁who ▁worked ▁on ▁the ▁project ▁was ▁American ▁computer ▁pione er ▁Harry ▁Hus key . ▁A ▁commercial ▁spin - off , ▁DE U CE ▁was ▁manufact ured ▁by ▁English ▁Electric ▁Comput ers ▁and ▁became ▁one ▁of ▁the ▁best - s elling ▁machines ▁of ▁the ▁ 1 9 5 0 s . ▁ ▁Metro log y ▁ ▁The ▁National ▁Phys ical ▁Labor atory ▁is ▁involved ▁with ▁new ▁develop ments ▁in ▁met ro log y , ▁such ▁as ▁research ing ▁met ro log y ▁for , ▁and ▁standard ising , ▁nan ote chn ology . ▁It ▁is ▁mainly ▁based ▁at ▁the ▁Ted d ington ▁site ,