In my dim memory of a conversation I had with Geoff Browne, he suggested the caravan was an experiment by Tillair in joining the pressure groups of the day that wanted the CAA to acquiesce to IFR RPT in modern turbine singles. But my experience of John Tilley suggests that he was not the "noble cause" sort of guy - more likely he had other work for it anyway (frieght, I suspect..). Nevertheless, I would be betting he was also more than a little curious anyway, as to whether the CAA would cave in to those that were, shall we say, more idealogical.