The prototype with test marks E-3 (later military serial number L2387) first flew on 18 June 1937 and was transferred to RAF Martlesham Heath for official evaluation. In the course of the trials, more equipment was added which increased the weight, and as a result, in an attempt to reduce weight, the dorsal turret was removed. The aircraft was also modified with small auxiliary fins fitted beneath the tailplane.
Despite the changes incorporated from the fifth aircraft, the type was deemed not suitable for training and the original order for 250 aircraft was reduced to only 50 aircraft, 20 of which were delivered as engineless airframes for ground training. The remaining aircraft served as communications and liaison aircraft, serving with No. 24 Sqn and numerous RAF Station Flights throughout the UK until early 1939, but all were grounded for use as instructional airframes in March 1939.