Captured reports

Hello, I’m new to this forum but hopefully you are the right people to ask.
Whilst researching a family member, I come across a reference to “ K E. 10139 CAPTURED GERMAN RECORDS”. I asked one of the senior members at 12oclock high, but he believes the files are being held by the RAF and are not available to the public.
Has anyone here managed to get hold of any captured any Luftwaffe records? Did the Germans keep any copies of these reports? Does anyone have access or know where/how I can get hold of a copy?
Thanks in advance for any help.
NM