The Condon Report:
2230-0330 LST. Weather: generally clear until 0300 LST on the 14th. (For details see Section IV.) 

The probability that anomalous propagation of radar signals may have been involved in this case seems to be small. One or two details are suggestive of AP, particularly the reported disappearance of the first track as the UFO appeared to over fly the Bentwaters GCA radar. Against this must be weighed the Lakenheath controller's statement that there was "little or no traffic or targets on scope," which is not at all suggestive of AP conditions, and the behavior of the target near Lakenheath -- apparently continuous and easily tracked. The "tailing" of the RAF fighter, taken alone, seems to indicate a possible ghost image, but this does not jibe with the report that the UFO stopped following the fighter, as the latter was returning to its base, and went off in a different direction. The radar operators were apparently careful to calculate the speed of the UFO from distances and elapsed times, and the speeds were reported as consistent from run to run, between stationary episodes. This behavior would be somewhat consistent with reflections from moving atmospheric layers -- but not in so many different directions. 

Visual mirage at Bentwaters seems to be out of the question because of the combined ground and airborne observations; the C47 pilot apparently saw the UFO below him. The visual objects do not seem to have been meteors; statements by the observers that meteors were numerous imply that they were able to differentiate the UFO from the meteors. 

In summary, this is the most puzzling and unusual case in the radar-visual files. The apparently rational, intelligent behavior of the UFO suggests a mechanical device of unknown origin as the most probable explanation of this sighting. However, in view of the inevitable fallibility of witnesses, more conventional explanations of this report cannot be entirely ruled out. 

Source: The Condon Report. page 245