Despite the best efforts of many (for which I am grateful), none hase ever been able to point to the piece of legislation which absolutely prohibits 'passengers' ie. non-operational crew from being in the flight deck of a non-UK registered aircraft inside UK airspace. I've seen that that door must be locked any time an engine is running and seen that none other than operating crew may be present on the flight of UK registered aircraft but no more that. Not even the great Google, Lycos, Ask etc. are any help. Ideas anyone?