Smokey
The article you mention is actually in Aeroplane (Feb 2006) not Flypast. I know this because I wrote it
The gist of the story (as you'll know, but others might not) is that in December 1940 the Air Attache in Sofia was duped by a man claiming to be Baur's father-in-law into believing that Baur was prepared to defect with Hitler on board. Since I've no doubt that Baur had no such intention (and, as I made clear in the article, there are many inconsistencies in the informants story) the article focusses on the RAF's preparations for the event. The target date for the flight was March 25, but the preparations were left in place until June - most probably because of Hess' arrival on 10th May.
The most curious thing about the tale, apart from the real identity and motives of the attaches informant, is the way in which the RAF seem to have treated the whole thing as a private enterprise. I've found nothing so far to indicate that Churchill, the Chiefs of Staff or the usual intlligence bodies were brought into the picture.
Even though the basis for the whole enterprise was clearly false, it's an interesting story so I've started the wheels in motion for a Freedom of Information Act request to get the release of some additional material, which may, but I suspect doesn't exist.
NiallC