Perhaps a slightly more realistic scenario has happened to me more than once. I am flying as PIC with a passenger who has an IMC rating and owns a share in the aircraft. Halfway through the trip the weather unexpectedly deteriorates and we cannot continue under VFR. I pass command to the other pilot so that we can legally continue. I have always logged only the time I was PIC and the normal T/O and landing times. Using this system I have completed a lot more flights in risky weather than I would have done as a sole PPL.