Continuity mistake: In the opening scenes while lost on her way to Sandringham, Diana drives a Porsche 911 with licence plate G580SGT. Later when she stops by the scarecrow the same car's plate has changed to J548LRP, it remains so for the rest of the movie. J548LRP was an actual plate used on a Mercedes SL500 that Princess Diana once owned.
Continuity mistake: Diana used wire cutters to deliberately cut her left upper arm, about 3" from her underarm. When she went to the mirror to wipe it, the cut looked bigger (not just from blood) and was about 2" lower on her arm. Afterwards, there was little to no sign of the cut. (01:16:37 - 01:20:52)