The lancair departed MC when the tower was closed. He reported his departure on area freq and it was at this point a potential conflict was recognised. It is interesting to note that he is not required to make this broadcast and if he did not the situation would have been far worse as the traffic would have been passed as a unidentified ac with no knowledge of the lancairs route or level. The 800 feet was reported in the esir, the 400 feet was the actual difference as derived from playing back the radar tapes.