 By September , several Blenheims were equipped with what was now officially known as AI Mk . I and training of the crews began with No. 25 Squadron at RAF Northolt . Robert Hanbury Brown , a physicist who would later work on radar in the US , and Keith Wood joined them in August 1939 , helping fitters keep the systems operational , and coming up with useful methods for interception . Near the end of August , Dowding visited the base and saw the radars in the nose and pointed out to Bowen that the enemy gunners would see the light from the CRTs and shoot the operator . The sets were re @-@ fitted once again , returning to the rear of the fuselage , which caused more delays . 
