Brian Trubshaw had been test flying Concorde for some time, before it was discovered that he only had a PPL
If UK rules are the same as here, I could see it as a possibility. As a test pilot he would not be employed in a capacity where he is flying commercial operations ie paying pax on board, or freight for a third party who is giving remuneration for the flight. Test flying by a company manufacturing the aircraft would possibly be seen as a private operation.