 The War Office examined the design and put the prototype through a series of trials during May and June 1938 ; the model was tested as a possible " light cruiser " since War Office light tank needs were already met by its predecessor , the Mark VI . The War Office then took the view that the tank was not acceptable as a light cruiser because the Nuffield A13 offered better speed and obstacle crossing performance . Despite this , it was decided that it was essential for some Tetrarchs to be produced , and it was suggested that they be brought in at the end of the light tank program . Accordingly , the War Office gave the Tetrarch the official General Staff specification number A17 , and , in November 1938 , accepted it for limited production after requesting a few minor changes which included the fitting of an external fuel tank to increase the tank 's range . 
 The War Office examined the design and put the prototype through a series of trials during May and June 1938 ; the model was tested as a possible " light cruiser " since War Office light tank needs <a href='uninflect' title='1'><mark>were</mark></a> already met by its predecessor , the Mark VI . The War Office then took the view that the tank <a href='negative_concord' title='2'><mark>was</mark></a> <a href='negative_concord' title='3'><mark>not</mark></a>acceptable as a light cruiser because the Nuffield A13 offered better speed and obstacle crossing performance . Despite this , it was decided that it was essential for some Tetrarchs to be produced , and it was suggested that they <a href='uninflect' title='4'><mark>be</mark></a> brought in at the end of the light tank program . Accordingly , the War Office gave the Tetrarch the official General Staff specification number A17 , and , in November 1938 , accepted it for limited production after requesting a few minor changes which included the fitting of an external fuel tank to increase the tank <a href='null_genetive' title='5'><mark>'s</mark></a>range . 
The War Office examined da design and put the prototype through a series of trials during May and June 1938 ; the model was tested as a possible " light cruiser " since War Office light tank needs was already met by its predecessor , tdaMark VI . The War Office then took the view dat the tank ain't acceptable as a light cruiser cuz the Nuffield A13 offered betta speed and obstacle crossing performance . Despite this , it was decided tdatit was essential fa some Tetrarchs to be produced , and it was suggested thdathey am brought in at the end of the light tank program . Accordingly , the War Office gave the Tetrarch the official General Staff specification number A17 , and , in November 1938 , accepted it ffirlimited production after requesting a few minor changes which included the fitting of an external fuel tank to increase thdaank  range .