Apollo+40: Tenth and final orbit?

Earlier at 23:56 EST/88:05 MET, Apollo 8 had been given the go from Mission Control for the critical Trans-Earth Injection (TEI) burn - the firing of the SPS engine that would if successful sent Apollo 8 on a long coast back to Earth. Should it fail, Borman, Lovell, and Anders would become a permanent fixture in Lunar orbit, along with their spacecraft.

At 00:42 EST Christmas morning, Apollo 8 passed behind the Moon for what was hopefully the last time. TEI would happen on the far-side...