▁at ▁a ▁slightly ▁faster ▁tempo ▁than ▁previously . ▁ ▁Production ▁details ▁The ▁original ▁series ▁were ▁all ▁produced ▁by ▁Th ames ▁Television ▁for ▁I TV . ▁The ▁first ▁and ▁second ▁series ▁were ▁recorded ▁on ▁ 2 " ▁quad ru plex ▁vide ot ape ▁at ▁Th ames ' ▁Ted d ington ▁Studios ▁in ▁London , ▁with ▁location ▁scenes ▁shot ▁in ▁Amsterdam ▁on ▁ 1 6 mm ▁film . ▁The ▁third ▁series ▁was ▁generally ▁made ▁on ▁location , ▁entirely ▁on ▁ 1 6 mm ▁film , ▁by ▁Th ames ' s ▁subs idi ary ▁E ust on ▁Films . ▁The ▁fourth ▁series ▁was ▁recorded ▁on ▁ 1 " ▁Pan ason ic ▁vide ot ape , ▁with ▁location ▁shooting ▁shot ▁on ▁ 3 5 mm ▁film . ▁Series ▁five ▁was ▁similarly ▁shot , ▁but ▁with ▁the ▁studio ▁recording ▁on ▁D - 3 ▁vide ot ape . ▁The ▁final ▁two ▁series ▁were ▁transm itted ▁in ▁s tere o ▁sound ▁using ▁the ▁N IC AM ▁system . ▁Network ▁released ▁all ▁five ▁series ▁on ▁Region ▁ 2 ▁DVD ▁on ▁ 2 2 ▁October ▁ 2 0 0 7 . ▁ ▁Epis odes ▁ ▁Series ▁ 1 ▁( 1 9 7 2 ) ▁ ▁Series ▁ 2 ▁( 1 9 7 3 ) ▁ ▁Series ▁ 3 ▁( 1 9 7 7 ) ▁ ▁Series ▁ 4 ▁( 1 9 9 1 ) ▁ ▁Series ▁ 5 ▁( 1 9 9 2 ) ▁ ▁Rev ival ▁( 2 0 2 0 ) ▁A ▁series ▁of ▁three ▁ 9 0 - min