When developing the AI23 radar for the Lightning there would have been a requirement for target aircraft to fly profiles to test the radar's capabilities. I think the radar was installed in modified Canberras IIRC. Certainly the FFU used a number of Canberras over the years. I wonder whether the RAF provided the target aircraft for these trials? Perhaps Meteors? I've lost touch with the FFU staff over the past 20 years so I'm not able to check.