Bose-x
I was thinking it looks like Pilot A wants Pilot B to say he was actually flying that trip, on the basis that A has no medical. B Agrees and all is squared away for a few days.
Then along comes the CAA man to interview Pilot B about an airspace infringemnet. Pilot B can hardly say "My defence to the charge is that I committed a different offence, that of falsifying a logbook!"